Three-plate camera and four-plate camera

ABSTRACT

A three-plate camera includes an IR prism that causes an IR image sensor to receive incident IR light of light from an observation part, a visible prism that causes a visible image sensor to receive incident visible light of light from the observation part, a specific prism that causes a specific image sensor to receive incident light of a specific wavelength band of light from the observation part, and a video signal processing unit that generates an IR video signal, a visible video signal, and a specific video signal of the observation part based on respective imaging outputs of the IR image sensor, the visible image sensor, and the specific image sensor, combines the IR video signal, the visible video signal, and the specific video signal, and outputs a combined video signal to a monitor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2020-074282 filed on Apr. 17, 2020, thecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a three-plate camera and a four-platecamera.

BACKGROUND ART

In recent years, attention has been paid to a method of performingdiagnosis in which at the time of surgery or examination, indocyaninegreen (ICG) is administered as a fluorescent reagent into a subject, ICGis excited by irradiation with excitation light or the like, and anear-infrared fluorescent image presented by ICG is imaged together witha subject image and is observed. For example, Patent Literature 1discloses an imaging device including a blue color separation prism thatreflects light of a blue component of incident light and a part ofnear-infrared light of a specific wavelength range and transmits therest of light, a red color separation prism that reflects light of a redcomponent and a part of near-infrared light of a specific wavelengthrange and transmits the rest of light, and a green color separationprism to which light transmitted through the red color separation prismis incident.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2016-75825

SUMMARY OF INVENTION

In Patent Literature 1, a light amount of the part of near-infraredlight of light from an affected part or the like is incident so as to bedistributed to each of a plurality of color separation prisms and isimaged. For this reason, for example, there is a problem that lightspecialized for a wavelength range of the near-infrared light cannot bereceived by a corresponding imaging element. Therefore, at the time ofsurgery or examination described above, it is difficult to output aclearer fluorescent image of an observation part to which a fluorescentreagent is administered, and there is room for improvement in terms ofmaking a doctor or the like more easily understand the affected part.

The present disclosure has been made in view of the above-describedcircumstances in the related art, and provides a three-plate camera anda four-plate camera that generate and output a clearer fluorescenceimage of an observation part to which a fluorescent reagent isadministered, and support easy understanding of an affected part for adoctor or the like.

The present disclosure provides a three-plate camera including: an IRprism that causes an IR image sensor to receive incident IR light oflight from an observation part; a visible prism that causes a visibleimage sensor to receive incident visible light of light from theobservation part; a specific prism that causes a specific image sensorto receive incident light of a specific wavelength band of light fromthe observation part; and a video signal processing unit that generatesan IR video signal, a visible video signal, and a specific video signalof the observation part based on respective imaging outputs of the IRimage sensor, the visible image sensor, and the specific image sensor,combines the IR video signal, the visible video signal, and the specificvideo signal, and outputs a combined video signal to a monitor.

Further, the present disclosure provides a three-plate camera including:a first visible prism that causes a first visible image sensor toreceive incident first visible light of light from an observation part;a second visible prism that causes a second visible image sensor toreceive incident second visible light of light from the observationpart; a specific prism that causes a specific image sensor to receiveincident light of a specific wavelength band of light from theobservation part; and a video signal processing unit that generates afirst visible video signal, a second visible video signal, and aspecific video signal of the observation part based on respectiveimaging outputs of the first visible image sensor, the second visibleimage sensor, and the specific image sensor, combines the first visiblevideo signal, the second visible video signal, and the specific videosignal, and outputs a combined video signal to a monitor.

Further, the present disclosure provides a four-plate camera including:an IR prism that causes an IR image sensor to receive incident IR lightof light from an observation part; a visible prism that causes a visibleimage sensor to receive incident visible light of light from theobservation part; a first specific prism that causes a first specificimage sensor to receive incident light of a first specific wavelengthband of light from the observation part; a second specific prism thatcauses a second specific image sensor to receive incident light of asecond specific wavelength band of light from the observation part; anda video signal processing unit that generates an IR video signal, avisible video signal, a first specific video signal, and a secondspecific video signal of the observation part based on respectiveimaging outputs of the IR image sensor, the visible image sensor, thefirst specific image sensor, and the second specific image sensor,combines the IR video signal, the visible video signal, the firstspecific video signal, and the second specific video signal, and outputsa combined video signal to a monitor.

Further, the present disclosure provides a four-plate camera including:a first visible prism that causes a first visible image sensor toreceive incident first visible light of light from an observation part;a second visible prism that causes a second visible image sensor toreceive incident second visible light of light from the observationpart; a first specific prism that causes a first specific image sensorto receive incident light of a first specific wavelength band of lightfrom the observation part; a second specific prism that causes a secondspecific image sensor to receive incident light of a second specificwavelength band of light from the observation part; and a video signalprocessing unit that generates a first visible video signal, a secondvisible video signal, a first specific video signal, and a secondspecific video signal of the observation part based on respectiveimaging outputs of the first visible image sensor, the second visibleimage sensor, the first specific image sensor, and the second specificimage sensor, combines the first visible video signal, the secondvisible video signal, the first specific video signal, and the secondspecific video signal, and outputs a combined video signal to a monitor.

According to the present disclosure, it is possible to generate andoutput a clearer fluorescent image of an observation part to which afluorescent reagent is administered, and to support easy understandingof an affected part for a doctor or the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an internal configuration exampleof a three-plate camera according to a first configuration example.

FIG. 2 is a block diagram illustrating an internal configuration exampleof a three-plate camera according to a second configuration example.

FIG. 3 is a block diagram illustrating an internal configuration exampleof a three-plate camera according to a third configuration example.

FIG. 4 is a block diagram illustrating an internal configuration exampleof a three-plate camera according to a fourth configuration example.

FIG. 5 is a block diagram illustrating an internal configuration exampleof a three-plate camera according to a fifth configuration example.

FIG. 6 is a table illustrating a combination example of configurationexamples of a three-plate camera according to a first embodiment.

FIG. 7 is a diagram illustrating an example of a structure of a spectralprism according to the first embodiment.

FIG. 8A is a graph illustrating an example of a spectral characteristicof a first reflecting film.

FIG. 8B is a graph illustrating an example of a spectral characteristicof a second reflecting film.

FIG. 8C is a graph illustrating another example of the spectralcharacteristic of the first reflecting film or the second reflectingfilm.

FIG. 8D is a graph illustrating another example of the spectralcharacteristic of the second reflecting film.

FIG. 8E is a graph illustrating another example of the spectralcharacteristic of the second reflecting film.

FIG. 9 is a graph illustrating an example of relationships between avisible light division ratio and sensitivity, a dynamic range, andresolution in a case where exposure time of second visible light andthat of first visible light are the same.

FIG. 10 is a graph illustrating an example of the relationships betweenthe visible light division ratio and the sensitivity, the dynamic range,and the resolution in a case where the exposure time of the secondvisible light and that of the first visible light are 10:1.

FIG. 11 is a graph illustrating an example of the relationships betweenthe visible light division ratio and the sensitivity, the dynamic range,and the resolution in a case where the exposure time of the secondvisible light and that of the first visible light are 100:1.

FIG. 12 is a graph illustrating an example of the relationships betweenthe visible light division ratio and the sensitivity, the dynamic range,and the resolution in a case where the exposure time of the secondvisible light and that of the first visible light are 1:10.

FIG. 13 is a diagram illustrating a display example on a monitor of avisible/IR combined video signal generated by the three-plate cameraaccording to the first embodiment.

FIG. 14 is a diagram illustrating another display example on the monitorof the visible/IR combined video signal generated by the three-platecamera according to the first embodiment.

FIG. 15 is a block diagram illustrating an internal configurationexample of a four-plate camera according to a seventh configurationexample.

FIG. 16 is a block diagram illustrating an internal configurationexample of a four-plate camera according to an eighth configurationexample.

FIG. 17 is a block diagram illustrating an internal configurationexample of a four-plate camera according to a ninth configurationexample.

FIG. 18 is a block diagram illustrating an internal configurationexample of a four-plate camera according to a tenth configurationexample.

FIG. 19 is a table illustrating a combination example of configurationexamples of a four-plate camera according to a second embodiment.

FIG. 20 is a diagram illustrating an example of a structure of aspectral prism according to the second embodiment.

DESCRIPTION OF EMBODIMENTS Technical Background of Embodiments

In Patent Literature 1, a light amount of a part of near-infrared lightof light from an affected part or the like is incident so as to bedistributed to each of a plurality of color separation prisms and isimaged. For this reason, for example, there is a problem that lightspecialized for a wavelength range of the near-infrared light cannot bereceived by a corresponding imaging element. Therefore, at the time ofsurgery or examination described above, it is difficult to output aclearer fluorescent image of an observation part to which a fluorescentreagent is administered, and there is room for improvement in terms ofmaking a doctor or the like more easily understand the affected part.

Therefore, in the following first embodiment, an example of athree-plate camera will be described that generates and outputs aclearer fluorescent image of an observation part to which a fluorescentreagent is administered, and that supports easy understanding of anaffected part for a doctor or the like.

In addition, Patent Literature 1 discloses a configuration in which apart of the near-infrared light is reflected in each of a plurality ofprisms (specifically, a blue color separation prism and a red colorseparation prism) among prisms constituting a color separation prism,and is received by each corresponding image sensor at a subsequentstage. Therefore, visible light having a wavelength of about 400 nm to800 nm cannot be reflected by the plurality of prisms constituting thecolor separation prism to be received by each corresponding image sensorat the subsequent stage, and it is difficult to obtain a clear imagedimage having a high dynamic range. Therefore, there is room forimprovement in terms of making the doctor or the like more easilyunderstand the affected part at the time of surgery or examinationdescribed above.

Therefore, in the following first embodiment, an example of athree-plate camera will be described that generates and outputs aclearer imaged image of an observation part having a high dynamic rangeand that supports easy understanding of an affected part for a doctor orthe like.

First Embodiment

Hereinafter, embodiments of a three-plate type camera and a four-platetype camera according to the present disclosure will be described indetail with reference to the drawings as appropriate. However, anunnecessarily detailed description may be omitted. For example, adetailed description of a well-known matter or a repeated description ofsubstantially the same configuration may be omitted. This is to avoidunnecessary redundancy in the following description and to facilitateunderstanding for those skilled in the art. The accompanying drawingsand the following description are provided for those skilled in the artto fully understand the present disclosure, and are not intended tolimit the subject matter described in the claims.

First Configuration Example

In the first configuration example, it is assumed that a light amount offirst visible light V1 incident on an imaging element 151 and a lightamount of second visible light V2 incident on an imaging element 152 aredifferent from each other.

FIG. 1 is a block diagram illustrating an internal configuration exampleof a three-plate camera 1 according to the first configuration example.The three-plate camera 1 includes a lens 11, a spectral prism 13,imaging elements 151, 152, and 153, and a video signal processing unit17. The video signal processing unit 17 includes camera signalprocessing units 191, 192, and 193, a long and short exposurecombination/wide dynamic range processing unit 21, and a visible/IRcombination processing unit 23.

The three-plate camera (see FIGS. 1, 2 and 4) according to a firstembodiment is used in, for example, a medical observation system thatirradiates a fluorescent reagent (for example, indocyanine green that isabbreviated as “ICG” in the following description) administered inadvance to an observation part (for example, an affected part) in asubject such as a patient with excitation light of a predeterminedwavelength band (for example, 760 nm to 800 nm) at the time of surgeryor examination, and that images the observation part emittingfluorescence at a long wavelength side (for example, 820 nm to 860 nm)based on the excitation light. An image (for example, a video of anobservation part) imaged by the three-plate camera is displayed by amonitor MN1 (see FIG. 13), and supports execution of a medical practiceby a user such as a doctor. Although an example in which the spectralprism 13 is used in, for example, the above-described medicalobservation system is described, the use thereof is not limited tomedical applications and may be industrial applications.

Although not illustrated in FIG. 1, a tip end portion from the lens 11of the three-plate camera 1 is configured with a scope that is to beinserted into an observation part (for example, an affected part. Thesame applies to the following). The scope is, for example, a main partof a medical instrument such as a rigid endoscope to be inserted into anobservation part, and is an elongated light guide member capable ofguiding light L1 from the observation part to the lens 11.

The lens 11 is attached on a target-facing side (tip end side) of thespectral prism 13, and concentrates the light L1 from the observationpart (for example, reflected light at the observation part).Concentrated light L2 is incident on the spectral prism 13.

The spectral prism 13 as an example of an optical component receives thelight L2 from the observation part, and disperses the light L2 into thefirst visible light V1, the second visible light V2, and IR light N1.The spectral prism 13 has a configuration in which a first prism 31 (forexample, an IR prism), a second prism 32 (for example, a visible prism),and a third prism 33 (for example, a visible prism) are bonded in order(see FIG. 7). The first visible light V1 is incident on the imagingelement 152 that is disposed so as to face the third prism 33. Thesecond visible light V2 is incident on the imaging element 151 that isdisposed so as to face the second prism 32. The IR light N1 is incidenton the imaging element 153 that is disposed so as to face the firstprism 31. A detailed example of a structure of the spectral prism 13will be described later with reference to FIG. 7.

The imaging element 151 as an example of a visible image sensorincludes, for example, a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) in which a plurality of pixels suitablefor imaging of visible light are arranged, and an exposure controlcircuit (not illustrated) using an electronic shutter. The imagingelement 151 is disposed so as to face the second prism 32 (for example,a visible prism) (see FIG. 7). The imaging element 151 performs imagingbased on the first visible light V1 incident over first exposure timethat is determined by the exposure control circuit based on an exposurecontrol signal CSH1 from the camera signal processing unit 191. Theimaging element 151 generates a video signal V1V of the observation partby imaging, and outputs the video signal V1V to the video signalprocessing unit 17.

The imaging element 152 as an example of a specific image sensorincludes, for example, a CCD or CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged, and an exposurecontrol circuit (not illustrated) using an electronic shutter. Theimaging element 152 is disposed so as to face the third prism 33 (forexample, a visible prism) (see FIG. 7). The imaging element 152 performsimaging based on the second visible light V2 incident over secondexposure time that is determined by the exposure control circuit basedon an exposure control signal CSH2 from the camera signal processingunit 192. The imaging element 152 generates a video signal V2V of theobservation part by imaging, and outputs the video signal V2V to thevideo signal processing unit 17.

The imaging element 153 as an example of an IR image sensor includes,for example, a CCD or a CMOS in which a plurality of pixels suitable forimaging of IR light are arranged. The imaging element 153 is disposed soas to face the first prism 31 (for example, an IR prism) (see FIG. 7).The imaging element 153 performs imaging based on the incident IR lightN1. The imaging element 153 generates a video signal N1V of theobservation part by imaging, and outputs the video signal N1V to thevideo signal processing unit 17.

The video signal processing unit 17 is configured with a processor suchas a digital signal processor (DSP) or a field-programmable gate array(FPGA), for example. Each of the camera signal processing units 191 to193, the long and short exposure combination/wide dynamic rangeprocessing unit 21, and the visible/IR combination processing unit 23 isimplemented by the processor described above.

The camera signal processing unit 191 performs various types of camerasignal processing using the video signal V1V from the imaging element151 to generate a first visible video signal V1VD of the observationpart, and outputs the first visible video signal V1VD to the long andshort exposure combination/wide dynamic range processing unit 21. Inaddition, the camera signal processing unit 191 generates the exposurecontrol signal CSH1 for determining the first exposure time of theimaging element 151 and outputs the generated exposure control signalCSH1 to the imaging element 151. The imaging element 151 controls thefirst exposure time of the first visible light V1 based on the exposurecontrol signal CSH1.

The camera signal processing unit 192 performs various types of camerasignal processing using the video signal V2V from the imaging element152 to generate a second visible video signal V2VD of the observationpart, and outputs the second visible video signal V2VD to the long andshort exposure combination/wide dynamic range processing unit 21. Here,in the first configuration example, the light amount of the firstvisible light V1 incident on the imaging element 151 is different fromthe light amount of the second visible light V2 incident on the imagingelement 152. Therefore, the first visible video signal V1VD from thecamera signal processing unit 191 and the second visible video signalV2VD from the camera signal processing unit 192 are different inbrightness (sensitivity). In addition, the camera signal processing unit192 generates the exposure control signal CSH2 for determining thesecond exposure time of the imaging element 152 and outputs thegenerated exposure control signal CSH2 to the imaging element 152. Theimaging element 152 controls the second exposure time of the secondvisible light V2 based on the exposure control signal CSH2. Althoughdetails will be described later, the first exposure time and the secondexposure time may be the same or different.

The camera signal processing unit 193 performs various types of camerasignal processing using the video signal N1V from the imaging element153 to generate an IR video signal N1VD of the observation part, andoutputs the IR video signal N1VD to the visible/IR combinationprocessing unit 23.

The long and short exposure combination/wide dynamic range processingunit 21 receives the two video signals having different brightness(sensitivity) (specifically, the first visible video signal V1VD fromthe camera signal processing unit 191 and the second visible videosignal V2VD from the camera signal processing unit 192) and combines thetwo video signals by superimposition, and generates a wide dynamic rangevideo signal VVD. That is, the long and short exposure combination/widedynamic range processing unit 21 can generate the wide dynamic rangevideo signal VVD whose dynamic range is wider than that of the firstvisible video signal V1VD or the second visible video signal V2VD bycombining the first visible video signal V1VD and the second visiblevideo signal V2VD having different brightness (sensitivity). The longand short exposure combination/wide dynamic range processing unit 21outputs the wide dynamic range video signal VVD to the visible/IRcombination processing unit 23.

The visible/IR combination processing unit 23 receives the wide dynamicrange video signal VVD from the long and short exposure combination/widedynamic range processing unit 21 and the IR video signal N1VD from thecamera signal processing unit 193, and combines the wide dynamic rangevideo signal VVD and the IR video signal N1VD by superimposition, andgenerates a visible/IR combined video signal IMVVD. The visible/IRcombination processing unit 23 may output the visible/IR combined videosignal IMVVD to the monitor MN1 or transmit the visible/IR combinedvideo signal IMVVD to a recording device (not illustrated) foraccumulation.

The monitor MN1 constitutes, for example, an image console (notillustrated) disposed in an operating room at the time of surgery orexamination, and displays the visible/IR combined video signal IMVVD ofthe observation part that is generated by the three-plate camera 1.Accordingly, the user, such as a doctor, visually recognizes thevisible/IR combined video signal IMVVD displayed on the monitor MN1, andthus can understand in detail a condition of a surrounding portion of asurgical field or the like according to a color video having the widedynamic range as well as a condition of a part emitting fluorescence inthe observation part. The recording device is, for example, a recordercapable of recording data of the visible/IR combined video signal IMVVDgenerated by the three-plate camera 1.

Second Configuration Example

In a second configuration example, it is assumed that the light amountof the first visible light V1 incident on the imaging element 151 andthe light amount of the second visible light V2 incident on the imagingelement 152 are substantially equal (in other words, there is littledifference). Therefore, the first visible video signal V1VD from thecamera signal processing unit 191 and the second visible video signalV2VD from the camera signal processing unit 192 are substantially thesame in brightness (sensitivity), and the first visible video signalV1VD and the second visible video signal V2VD having substantially thesame brightness (sensitivity) are subjected to combination processingcorresponding to pixel shift, so that a high-resolution video signalVVDA having high resolution can be generated.

FIG. 2 is a block diagram illustrating an internal configuration exampleof a three-plate camera 1A according to the second configurationexample. The three-plate camera 1A includes the lens 11, the spectralprism 13, the imaging elements 151, 152, and 153, and a video signalprocessing unit 17A. The video signal processing unit 17A includes thecamera signal processing units 191, 192, and 193, a pixel-shiftcombination/high-resolution processing unit 25, and a visible/IRcombination processing unit 23A. In the description of FIG. 2, the samecomponents as those in FIG. 1 are denoted by the same reference signs,and a description thereof will be simplified or omitted, and differentcontents will be described. In the description of a configuration inwhich the three-plate camera according to the first embodiment describedbelow is capable of imaging at least two channels of visible light(specifically, the first configuration example, the second configurationexample, a fifth configuration example, and a sixth configurationexample), the long and short exposure combination/wide dynamic rangeprocessing unit 21 and the like may not only perform processing forhaving a color video having a wide dynamic range described in the firstconfiguration example, but also perform the high-resolution processing(see the above description) performed by the pixel-shiftcombination/high-resolution processing unit 25 in the secondconfiguration example. Further, in the description of the configurationin which the three-plate camera according to the first embodimentdescribed below is capable of imaging at least two channels of visiblelight (see the above description), the pixel-shiftcombination/high-resolution processing unit 25 may be used in place ofthe long and short exposure combination/wide dynamic range processingunit 21 and the like.

In the three-plate camera 1A, a high-resolution video signal VVDA bypixel shift is generated in the video signal processing unit 17A. Forthis reason, in the spectral prism 13, when the imaging element 151 onwhich the first visible light V1 is incident and the imaging element 152on which the second visible light V2 is incident are bonded to thesecond prism 32 and third prism 33 correspondingly, it is necessary tobond the imaging element 151 and the imaging element 152 to each othersuch that positions thereof are shifted by an optically half pixel (forexample, in a horizontal direction or in a vertical direction or in bothdirections). Accordingly, the high-resolution video signal VVDA by pixelshift can be generated in the pixel-shift combination/high-resolutionprocessing unit 25 based on imaging of the imaging elements 151 and 152that are arranged to be shifted by an optically half pixel (see theabove description).

The camera signal processing unit 191 generates the first visible videosignal V1VD of the observation part, and outputs the first visible videosignal V1VD to the pixel-shift combination/high-resolution processingunit 25.

The camera signal processing unit 192 generates the second visible videosignal V2VD of the observation part, and outputs the second visiblevideo signal V2VD to the pixel-shift combination/high-resolutionprocessing unit 25.

The pixel-shift combination/high-resolution processing unit 25 receivesthe two video signals having substantially the same brightness(sensitivity) (specifically, the first visible video signal V1VD fromthe camera signal processing unit 191 and the second visible videosignal V2VD from the camera signal processing unit 192) as describedabove. The pixel-shift combination/high-resolution processing unit 25performs combination processing of the two received video signals (thatis, combination of the first visible video signal V1VD generated by thecamera signal processing unit 191 based on the imaging of the imagingelement 151 bonded to the second prism 32 and the second visible videosignal V2VD generated by the camera signal processing unit 192 based onthe imaging of the imaging element 152 bonded to the third prism 33),and generates the high-resolution video signal VVDA. The pixel-shiftcombination/high-resolution processing unit 25 can generate thehigh-resolution video signal VVDA having a higher resolution than thefirst visible video signal V1VD or the second visible video signal V2VDby performing the combination processing (see the above description) ofthe two received video signals. The pixel-shiftcombination/high-resolution processing unit 25 outputs thehigh-resolution video signal VVDA to the visible/IR combinationprocessing unit 23A.

The visible/IR combination processing unit 23A receives thehigh-resolution video signal VVDA from the pixel-shiftcombination/high-resolution processing unit 25 and the IR video signalN1VD from the camera signal processing unit 193 and combines the twosignals by superimposition, and generates a visible/IR combined videosignal IMVVDA. The visible/IR combination processing unit 23A may outputthe visible/IR combined video signal IMVVDA to the monitor MN1 ortransmit the visible/IR combined video signal IMVVDA to a recordingdevice (not illustrated) for accumulation.

Third Configuration Example

In a third configuration example, it is assumed that imaging isperformed by using an imaging element capable of imaging each of twodifferent wavelength bands among wavelength bands of near-infrared (IR)light using two channels (for example, imaging elements 151B and 153Billustrated in FIG. 3). Therefore, by appropriately superimposing afirst IR video signal N2VD based on first IR light N2 imaged by theimaging element 151B and a second IR video signal N3VD based on secondIR light N3 imaged by the imaging element 153B, it is possible togenerate a video signal that allows identifying a more detailed state ofan affected part as compared with a configuration (for example, thefirst configuration example and the second configuration example) inwhich the IR light is imaged only by one channel.

FIG. 3 is a block diagram illustrating an internal configuration exampleof a three-plate camera 1B according to the third configuration example.The three-plate camera 1B includes the lens 11, the spectral prism 13,the imaging elements 151B, 152, and 153B, and a video signal processingunit 17B. The video signal processing unit 17B includes camera signalprocessing units 191B, 192B, and 193B, and a visible/IR combinationprocessing unit 23B. In the description of FIG. 3, the same componentsas those in FIG. 1 or 2 are denoted by the same reference signs, and adescription thereof will be simplified or omitted, and differentcontents will be described.

The three-plate camera 1B is used in, for example, a medical observationsystem that irradiates a plurality of types of fluorescent reagents (forexample, ICG) administered in advance to observation parts (for example,an affected part) in a subject such as a patient with excitation lightof a predetermined wavelength band at the time of surgery orexamination, and that images the observation parts emitting fluorescenceat a long wavelength side (for example, 700 nm to 800 nm and 800 nm to900 nm) based on the excitation light. An image (for example, a video ofan observation part) imaged by the three-plate camera 1B is displayed bythe monitor MN1 (see FIG. 14), and supports execution of a medicalpractice by a user such as a doctor.

The spectral prism 13 receives the light L2 from the observation part,and disperses the light L2 into the first IR light N2, visible light V3,and the second IR light N3. The spectral prism 13 has a configuration inwhich the first prism 31 (for example, an IR prism), the second prism 32(for example, an IR prism), and the third prism 33 (for example, avisible prism) are bonded in order (see FIG. 7). The first IR light N2is incident on the imaging element 151B that is disposed so as to facethe second prism 32. The visible light V3 is incident on the imagingelement 152 that is disposed so as to face the third prism 33. Thesecond IR light N3 is incident on the imaging element 153B that isdisposed so as to face the first prism 31. A detailed example of astructure of the spectral prism 13 will be described later withreference to FIG. 7.

The imaging element 151B as an example of an IR image sensor includes,for example, a CCD or a CMOS in which a plurality of pixels suitable forimaging of IR light are arranged. The imaging element 151B is disposedso as to face the second prism 32 (for example, an IR prism) (see FIG.7). The imaging element 151B performs imaging based on the incidentfirst IR light N2. The imaging element 151B generates a video signal N2Vof the observation part by imaging, and outputs the video signal N2V tothe video signal processing unit 17B.

The imaging element 153B as an example of an IR image sensor includes,for example, a CCD or a CMOS in which a plurality of pixels suitable forimaging of IR light are arranged. The imaging element 153B is disposedso as to face the first prism 31 (for example, an IR prism) (see FIG.7). The imaging element 153B performs imaging based on the incidentsecond IR light N3. The imaging element 153B generates a video signalN3V of the observation part by imaging, and outputs the video signal N3Vto the video signal processing unit 17B.

The video signal processing unit 17B is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191B to 193B and the visible/IR combination processing unit 23B isimplemented by the processor described above.

The camera signal processing unit 191B performs various types of camerasignal processing using the video signal N2V from the imaging element151B to generate the IR video signal N2VD of the observation part, andoutputs the IR video signal N2VD to the visible/IR combinationprocessing unit 23B. Although details will be described later, the firstIR video signal N2VD and the second IR video signal N3VD have differentwavelengths of incident light used for imaging (see FIGS. 8D and 8E).

The camera signal processing unit 192B performs various types of camerasignal processing using a video signal V3V from the imaging element 152to generate a visible video signal V3VD of the observation part, andoutputs the visible video signal V3VD to the visible/IR combinationprocessing unit 23B.

The camera signal processing unit 193B performs various types of camerasignal processing using the video signal N3V from the imaging element153B to generate the second IR video signal N3VD of the observationpart, and outputs the second IR video signal N3VD to the visible/IRcombination processing unit 23B.

The visible/IR combination processing unit 23B receives the first IRvideo signal N2VD from the camera signal processing unit 191B, thevisible video signal V3VD from the camera signal processing unit 192B,and the second IR video signal N3VD from the camera signal processingunit 193B, and combines the three signals by superimposition, andgenerates a visible/IR combined video signal IMVVDB. The visible/IRcombination processing unit 23B may output the visible/IR combined videosignal IMVVDB to the monitor MN1 or transmit the visible/IR combinedvideo signal IMVVDB to a recording device (not illustration) foraccumulation.

Fourth Configuration Example

In a fourth configuration example, it is assumed that imaging isperformed by using an imaging element capable of imaging a plurality ofdifferent wavelength bands of visible light, IR light, and ultra violet(UV) light using three channels. Therefore, by superimposing videosignals imaged by imaging elements 151C, 152, and 153, it is possible togenerate a video signal that allows identifying a detailed state of anaffected part by imaging of light in various wavelength bands.

FIG. 4 is a block diagram illustrating an internal configuration exampleof a three-plate camera 1C according to the fourth configurationexample. The three-plate camera 1C includes the lens 11, the spectralprism 13, the imaging elements 151C, 152, and 153, and a video signalprocessing unit 17C. The video signal processing unit 17C includescamera signal processing units 191C, 192B, and 193, and a visible/IRcombination processing unit 23C. In the description of FIG. 4, the samecomponents as those in FIGS. 1 to 3 are denoted by the same referencesigns, and a description thereof will be simplified or omitted, anddifferent contents will be described.

The spectral prism 13 receives the light L2 from an observation part,and disperses the light L2 into UV light U1, the visible light V3, andthe IR light N1. The spectral prism 13 has a configuration in which thefirst prism 31 (for example, an IR prism), the second prism 32 (forexample, an UV prism), and the third prism 33 (for example, a visibleprism) are bonded in order (see FIG. 7). The UV light U1 is incident onthe imaging element 151C that is disposed so as to face the second prism32. The visible light V3 is incident on the imaging element 152 that isdisposed so as to face the third prism 33. The IR light N1 is incidenton the imaging element 153 that is disposed so as to face the firstprism 31. A detailed example of a structure of the spectral prism 13will be described later with reference to FIG. 7.

The imaging element 151C as an example of a specific image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of UV light are arranged. The imaging element 151Cis disposed so as to face the second prism 32 (for example, a UV prism)(see FIG. 7). The imaging element 151C performs imaging based on theincident UV light U1. The imaging element 151C generates a video signalU1V of the observation part by imaging, and outputs the video signal U1Vto the video signal processing unit 17C.

The video signal processing unit 17C is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191C, 192B and 193 and the visible/IR combination processing unit23C is implemented by the processor described above.

The camera signal processing unit 191C performs various types of camerasignal processing using the video signal U1V from the imaging element151C to generate a UV video signal U1VD of the observation part, andoutputs the UV video signal U1VD to the visible/IR combinationprocessing unit 23C.

The visible/IR combination processing unit 23C receives the UV videosignal U1VD from the camera signal processing unit 191C, the visiblevideo signal V3VD from the camera signal processing unit 192B, and theIR video signal N1VD from the camera signal processing unit 193 andcombines the three signals by superimposition, and generates avisible/IR combined video signal IMVVDC. The visible/IR combinationprocessing unit 23C may output the visible/IR combined video signalIMVVDC to the monitor MN1 or transmit the visible/IR combined videosignal IMVVDC to a recording device (not illustration) for accumulation.

Fifth Configuration Example

In a fifth configuration example, it is assumed that imaging isperformed by using an imaging element capable of imaging a wavelengthband of visible light using three channels (for example, imagingelements 151, 152, and 153D illustrated in FIG. 5), and light amounts ofvisible light incident on respective imaging elements are different fromeach other. Accordingly, it is possible to generate a video signal thatallows identifying in detail a condition of a surrounding portion of asurgical field or the like according to a color video having anobservation part or a high dynamic range in a periphery thereof.

FIG. 5 is a block diagram illustrating an internal configuration exampleof a three-plate camera 1D according to the fifth configuration example.The three-plate camera 1D includes the lens 11, the spectral prism 13,imaging elements 151, 152, and 153D, and a video signal processing unit17D. The video signal processing unit 17D includes camera signalprocessing units 191, 192, and 193D and a long and short exposurecombination/wide dynamic range processing unit 21D. In the descriptionof FIG. 5, the same components as those in FIGS. 1 to 4 are denoted bythe same reference signs, and a description thereof will be simplifiedor omitted, and different contents will be described.

The three-plate camera 1D is used in, for example, a medical observationsystem that obtains a more clear image of an observation part (forexample, an affected part) in a subject such as a patient or a surgicalfield of a periphery thereof than a normal color video (in other words,having a higher dynamic range than a normal color video) at the time ofsurgery or examination. An image (for example, a video of theobservation part) imaged by the three-plate camera 1D is displayed bythe monitor MN1, and supports execution of a medical practice by a usersuch as a doctor.

The spectral prism 13 receives the light L2 from the observation partand disperses the light L2 into the first visible light V1, the secondvisible light V2, and third visible light V4. The spectral prism 13 hasa configuration in which the first prism 31 (for example, a visibleprism), the second prism 32 (for example, a visible prism), and thethird prism 33 (for example, a visible prism) are bonded in order (seeFIG. 7). The first visible light V1 is incident on the imaging element153D that is disposed so as to face the first prism 31 (for example, avisible prism). The second visible light V2 is incident on the imagingelement 151 that is disposed so as to face the second prism 32 (forexample, a visible prism). The third visible light V4 is incident on theimaging element 152 that is disposed so as to face the third prism 33(for example, a visible prism). A detailed example of a structure of thespectral prism 13 will be described later with reference to FIG. 7.

The imaging element 153D as an example of a first visible image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged. The imaging element153D is disposed so as to face the first prism 31 (for example, anexample of a first visible prism) (see FIG. 7). The imaging element 153Dperforms imaging based on the incident first visible light V1. Theimaging element 153D generates the video signal V1V of the observationpart by imaging, and outputs the video signal V1V to the video signalprocessing unit 17D.

The imaging element 151 as an example of a second visible image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged. The imaging element151 is disposed so as to face the second prism 32 (an example of thesecond visible prism) (see FIG. 7). The imaging element 151 performsimaging based on the incident second visible light V2. The imagingelement 151 generates the video signal V2V of the observation part byimaging, and outputs the video signal V2V to the video signal processingunit 17D.

The imaging element 152 as an example of a specific image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged. The imaging element152 is disposed so as to face the third prism 33 (an example of aspecific prism) (see FIG. 7). The imaging element 152 performs imagingbased on the incident third visible light V4. The imaging element 152generates a video signal V4V of the observation part by imaging, andoutputs the video signal V4V to the video signal processing unit 17D.

The video signal processing unit 17D is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191, 192, and 193D and the long and short exposurecombination/wide dynamic range processing unit 21D is implemented by theprocessor described above.

The camera signal processing unit 193D performs various types of camerasignal processing using the video signal V1V from the imaging element153D to generate a third visible video signal V1VD of the observationpart, and outputs the third visible video signal V1VD to the long andshort exposure combination/wide dynamic range processing unit 21D. Inaddition, the camera signal processing unit 193D generates an exposurecontrol signal CSH3 for determining third exposure time of the imagingelement 153D and outputs the generated exposure control signal CSH3 tothe imaging element 153D. The imaging element 153D controls the thirdexposure time of the first visible light V1 based on the exposurecontrol signal CSH3.

The long and short exposure combination/wide dynamic range processingunit 21D receives three video signals having different brightness(sensitivity) (specifically, a first visible video signal V2VD from thecamera signal processing unit 191, a second visible video signal V4VDfrom the camera signal processing unit 192, and the third visible videosignal V1VD from the camera signal processing unit 193D) and combinesthe three video signals by superimposition, and generates a wide dynamicrange video signal VVDD. That is, by combining the first visible videosignal V2VD, the second visible video signal V4VD, and the third visualvideo signal V1VD having different brightness (sensitivity), the longand short exposure combination/wide dynamic range processing unit 21Dcan generate the wide dynamic range video signal VVDD having a widerdynamic range than the first visible video signal V2VD, the secondvisible video signal V4VD, or the third visible video signal V1VD. Thelong and short exposure combination/wide dynamic range processing unit21D may output the wide dynamic range video signal VVDD to the monitorMN1 or transmit the wide dynamic range video signal VVDD to a recordingdevice (not illustrated) for accumulation.

FIG. 6 is a table illustrating a combination example of configurationexamples of the three-plate camera according to the first embodiment. InFIG. 6, the first configuration example is described with reference toFIG. 1, the second configuration example is described with reference toFIG. 2, the third configuration example is described with reference toFIG. 3, the fourth configuration example is described with reference toFIG. 4, and the fifth configuration example is described with referenceto FIG. 5. As the three-plate camera according to the first embodiment,as a modification of the first configuration example or the secondconfiguration example (that is, a sixth configuration example), thelight incident on the first prism 31 may be UV light. That is, in thedescription of FIGS. 1 and 2, the “IR light” may be replaced with “UVlight”, the “video signal N1V” may be replaced with “video signal U1V”,and the “IR video signal N1VD” may be replaced with “UV video signalU1VD”.

FIG. 7 is a diagram illustrating an example of a structure of thespectral prism 13 according to the first embodiment. As described above,the spectral prism 13 has a configuration in which the first prism 31,the second prism 32, and the third prism 33 are bonded in this order.The first prism 31, the second prism 32, and the third prism 33 areassembled in order in an optical axis direction of the light L2concentrated by the lens 11. Here, the optical axis direction is adirection in which the light L2 is incident perpendicularly on anincidence surface 31 a of the first prism 31. In the first configurationexample to the sixth configuration example described above, the roles(in other words, functions and applications) of the first prism 31, thesecond prism 32, and the third prism 33 may be the same or different.

First, the first prism 31 is exemplified as an IR prism (see the firstto fourth configuration examples). However, the first prism 31 is notlimited to an IR prism, and may be a visible prism (see the fifthconfiguration example) or a UV prism (see the sixth configurationexample).

The IR prism includes the incidence surface 31 a on which the light L2is incident, a reflecting surface 31 b on which a first reflecting filmFLM1 (for example, a dichroic mirror) for reflecting IR light in thelight L2 is formed, and an emission surface 31 c from which the IR lightis emitted. The first reflecting film FLM1 is formed on the reflectingsurface 31 b by vapor deposition or the like, and reflects IR light (forexample, IR light in a wavelength band of 800 nm or more) in the lightL2, and transmits light (for example, UV light of about 300 nm to 400 nmor visible light of about 400 nm to 800 nm) that is not the IR light inthe light L2 (see FIG. 8A). The IR light is totally reflected by theincidence surface 31 a after being reflected by the reflecting surface31 b, and is incident on the imaging element 153 through the emissionsurface 31 c. In this way, since the IR prism is disposed as the firstprism 31, the IR component light in the light L2 from an observationpart is imaged on the most target-facing side (that is, the observationpart side) of the spectral prism 13. Compared with a case where the IRcomponent light is imaged at a rear stage side (that is, a base endside) of the spectral prism 13, attenuation of a light amount due toreflection or the like does not occur, and a condition of an affectedpart based on fluorescence emission of a fluorescent reagent can be moreclearly identified.

FIG. 8A is a graph illustrating an example of a spectral characteristicof the first reflecting film FLM1. In FIG. 8A, the horizontal axisrepresents wavelength [nm: nanometers], and the vertical axis representsreflectance or transmittance. A characteristic TP1 indicates thetransmittance of the first reflecting film, and according to thecharacteristic TP1, the first reflecting film FLM1 can transmit light ofabout 300 nm to 800 nm. A characteristic RF1 indicates the reflectanceof the first reflecting film FLM1, and according to the characteristicRF1, the first reflecting film FLM1 can reflect IR light of 800 nm ormore. Therefore, all of the IR light of a light amount represented byarea AR1 (in other words, the IR light in the light L2) can be incidenton the imaging element 153.

Next, the second prism 32 is exemplified as a visible prism (see thefirst, second, fifth, and sixth configuration examples). However, thesecond prism 32 is not limited to a visible prism, and may be an IRprism (see the third configuration example) or a UV prism (see thefourth configuration example).

The visible prism includes an incidence surface 32 a on which lighttransmitted through the first reflecting film FLM1 is incident, areflecting surface 32 b on which a second reflecting film FLM2 (forexample, a beam splitter) for reflecting a light amount of a part of thetransmitted light is formed, and an emission surface 32 c through whichreflected visible light of the light amount of the part of thetransmitted light is emitted. The second reflecting film FLM2 is formedon the reflecting surface 32 b by vapor deposition or the like, reflectsvisible light having a light amount of a part of visible light incidenton the incidence surface 32 a (for example, about 20% of the lightincident on the incidence surface 32 a), and transmits visible lighthaving the remaining light amount (for example, about 80% of the lightincident on the incidence surface 32 a) (see FIG. 8B). The part ofvisible light is totally reflected by the incidence surface 32 a afterbeing reflected by the reflecting surface 32 b, and is incident on theimaging element 151 through the emission surface 32 c. The proportion ofthe visible light reflected by the second reflecting film FLM2 is notlimited to 20%, and may be, for example, in a range of about 1% to 30%.

FIG. 8B is a graph illustrating an example of a spectral characteristicof the second reflecting film FLM2. In FIG. 8B, the horizontal axisrepresents wavelength [nm: nanometers], and the vertical axis representsreflectance or transmittance. A characteristic TP2 indicates thetransmittance of the second reflecting film, and according to thecharacteristic TP2, the second reflecting film FLM2 can transmit 80% ofthe visible light of about 400 nm to 800 nm. A characteristic RF2indicates the reflectance of the second reflecting film FLM2, andaccording to the characteristic RF2, the second reflecting film FLM2 canreflect 20% of visible light of about 400 to 800 nm. Therefore, visiblelight of a light amount indicated by area AR2 (that is, 20% of visiblelight (100%) incident on the incidence surface 32 a) can be incident onthe imaging element 151. In a case where the third prism 33, which willbe described later, is a visible prism, the 80% visible lighttransmitted through the second reflecting film FLM2 transmits throughthe third prism 33 and be incident on the imaging element 152.

In the spectral prism 13 corresponding to the second configurationexample (see FIG. 2), the second reflecting film FLM2 reflects visiblelight having a light amount of a part of visible light incident on theincidence surface 32 a (for example, about 50% of the light incident onthe incidence surface 32 a), and transmits visible light having theremaining light amount (for example, about 50% of the light incident onthe incidence surface 32 a). The proportion of the visible lightreflected by the second reflecting film FLM2 in this case is not limitedto 50%, and may be, for example, in a range of about 30% to 50%.Similarly, in a case where the third prism 33, which will be describedlater, is a visible prism, the 50% visible light transmitted through thesecond reflecting film FLM2 transmits through the third prism 33 and isincident on the imaging element 152.

FIG. 8C is a graph illustrating another example of the spectralcharacteristic of the first reflecting film or the second reflectingfilm. In FIG. 8C, the horizontal axis represents wavelength [nm:nanometers], and the vertical axis represents reflectance ortransmittance. A characteristic TP3 indicates the transmittance of thefirst reflecting film or the second reflecting film, and according tothe characteristic TP3, the first reflecting film FLM1 or the secondreflecting film FLM2 can transmit visible light of about 400 nm to 800nm. A characteristic RF3 indicates the reflectance of the firstreflecting film FLM1 or the second reflecting film FLM2, and accordingto the characteristic RF3, the first reflecting film FLM1 or the secondreflecting film FLM2 can reflect UV light of about 300 nm to 400 nm.Therefore, the UV light of a light amount indicated by area AR3 can beincident on the imaging element 151 or the imaging element 153.

Next, the third prism 33 is exemplified as a visible prism (see thefirst to sixth configuration examples). However, the third prism 33 isnot limited to a visible prism, and may be an IR prism or a UV prism.

The visible prism includes an incidence surface 33 a on which light (forexample, visible light) transmitted through the second reflecting filmFLM2 is incident, and an emission surface 33 c from which thetransmitted light is emitted. The visible light is incident on theimaging element 152 through the emission surface 33 c.

FIGS. 8D and 8E are graphs illustrating another example of the spectralcharacteristic of the second reflecting film FLM2. In FIGS. 8D and 8E,the horizontal axis represents wavelength [nm: nanometers], and thevertical axis represents reflectance or transmittance. A characteristicTP4 indicates the transmittance (light of 300 nm to 700 nm can transmit)of the second reflecting film FLM2 of the spectral prism 13 according tothe third configuration example (see FIG. 3), and a characteristic RF4indicates the reflectance (light of 700 nm to 800 nm can be reflected)of the second reflecting film FLM2 of the spectral prism 13 according tothe third configuration example (see FIG. 3). According to thecharacteristics TP4 and RF4, the second reflecting film FLM2 of thespectral prism 13 according to the third configuration example (see FIG.3) can reflect IR light of about 700 nm to 800 nm and transmit UV lightof 300 nm to 400 nm and visible light of 400 nm to 700 nm. Therefore,the IR light of a light amount indicated by area AR4 can be incident onthe imaging element 151. As illustrated in FIG. 8E, the secondreflecting film FLM2 of the spectral prism 13 according to the thirdconfiguration example (see FIG. 3) can reflect the IR light of about 700nm to 800 nm and transmit the UV light of 300 nm to 400 nm and thevisible light of 400 nm to 700 nm. The UV light or visible light havinga light amount indicated by area AR5 can be incident on the imagingelement 152.

FIG. 9 is a graph illustrating an example of relationships between avisible light division ratio and sensitivity GAN1, a dynamic range DRG1,and resolution RSO1 in a case where exposure time of the second visiblelight V2 and exposure time of the first visible light V1 are the same.The horizontal axis in FIG. 9 represents the visible light divisionratio, in other words, a proportion at which the light transmittedthrough the first reflecting film FLM1 (for example, visible light) isreflected by the second reflecting film FLM2 in the first configurationexample (see FIG. 1) or the second configuration example (see FIG. 2).For example, when the visible light division ratio is 10% (that is,90:10), the second reflecting film FLM2 reflects 10% of visible light ofthe light transmitted through the first reflecting film FLM1, andtransmits 90% of the visible light. That is, a light amount of thesecond visible light V2:a light amount of the first visible light V1 is90:10. Other visible light division ratios can also be considered in thesame manner as the specific example described above. The vertical axisin FIG. 9 represents the sensitivity GAN1, the dynamic range DRG1, andthe resolution RSO1 of the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA generated in the video signalprocessing units 17 and 17A.

FIG. 9 illustrates an example in which exposure time of each of theimaging elements 152 and 151 is controlled to be the same by anelectronic shutter. Therefore, it is considered that the sensitivityGAN1 changes in accordance with a characteristic (for example, a linearfunction) that: the sensitivity GAN1 increases as the visible lightdivision ratio decreases, is maximum when the visible light divisionratio is minimum (for example, the sensitivity GAN1 is most bright at amaximum (100%) when the visible light division ratio is 0%) and isminimum (the darkest at 50%) when the visible light division ratio is50%. This is because, among brightness of the first visible video signalV1VD based on the first visible light V1 and brightness of the secondvisible video signal V2VD based on the second visible light V2, thesensitivity is determined by brightness of the brighter second visiblelight V2.

It is considered that the dynamic range DRG1 changes similarly inaccordance with a characteristic that: the dynamic range DRG1 increasesas the visible light division ratio decreases in a range larger than 0(for example, the dynamic range DRG1 is about +80 dB when the visiblelight division ratio is 0.01%) and is minimum (for example, 0 dB) whenthe visible light division ratio is 50%. This is because, in the widedynamic range video signal VVD or the high-resolution video signal VVDA,a difference between a dark portion and a bright portion is more likelyto widen as the visible light division ratio decreases.

In contrast, it is considered that the resolution RSO1 changes inaccordance with a characteristic that: the resolution RSO1 decreases asthe visible light division ratio decreases, is minimum when the visiblelight division ratio is minimum (for example, the resolution RSO1 is 1times when the visible light division ratio is 0%), and is maximum (forexample, 1.4 times) when the visible light division ratio is 50%. Thisis because as the visible light division ratio increases, a differencein pixel value between adjacent pixels decreases, and it is more likelyto realize high resolution by pixel shift.

FIG. 10 is a graph illustrating an example of relationships between thevisible light division ratio and sensitivity GAN2, a dynamic range DRG2,and resolution RSO2 in a case where exposure time of the second visiblelight V2 and that of the first visible light V1 are 10:1. The horizontalaxis in FIG. 10 represents the visible light division ratio, and is thesame as the description of FIG. 9, and thus the description thereof willbe omitted. The vertical axis in FIG. 10 represents the sensitivityGAN2, the dynamic range DRG2, and the resolution RSO2 of the widedynamic range video signal VVD or the high-resolution video signal VVDAgenerated in the video signal processing units 17 and 17A.

FIG. 10 illustrates an example in which a difference is provided suchthat exposure time of the imaging element 152 and that of the imagingelement 151 are in a ratio of 10:1 by the electronic shutter. Similarlyto the sensitivity GAN1 illustrated in FIG. 9, it is considered that thesensitivity GAN2 changes in accordance with a characteristic (forexample, a linear function) that: the sensitivity GAN2 increases as thevisible light division ratio decreases, is maximum when the visiblelight division ratio is minimum (for example, the sensitivity GAN2 ismost bright at a maximum (100%) when the visible light division ratio is0%) and is minimum (the darkest at 50%) when the visible light divisionratio is 50%. This is because a result obtained by multiplying the ratio10:1 of the exposure time of the imaging element 152 to the exposuretime of the imaging element 151 by a ratio of light amount of the secondvisible light V2 to a light amount of the first visible light V1 is aratio of brightness of the second visible video signal V2VD tobrightness of the first visible video signal V1VD, and the sensitivityis determined by the brightness of the brighter second visible videosignal V2VD.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are, for example, in aratio of 10:1 as compared with a case where the exposure time of theimaging element 152 and that of the imaging element 151 are the same, itis considered that, in the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA, a difference between a bright portionand a dark portion can be more clearly exhibited, and the dynamic rangecan be further obtained. Accordingly, it is considered that the dynamicrange DRG2 changes in accordance with a characteristic that: the dynamicrange DRG2 increases as the visible light division ratio decreases in arange larger than 0 (for example, the dynamic range DRG2 is about +80 dBwhen the visible light division ratio is 0.1%) and is minimum (forexample, +20 dB) when the visible light division ratio is 50%. That is,in the example of FIG. 10, even at a minimum value, +20 dB can beobtained.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are in a ratio of 10:1by an electronic shutter, for example, when the visible light divisionratio is 10% (the second visible light V2:the first visible lightV1=90:10), it is considered that a light amount incident on the imagingelement 151:a light amount incident on the imaging element 152=100:1.That is, it can be considered that, in the first visible light V1, adark portion is not substantially reflected, and in the second visiblelight V2, a bright portion is not substantially reflected, and thus itis substantially difficult to gain resolution when the first visiblelight V1 and the second visible light V2 are superimposed. Therefore, itis considered that the resolution RSO2 changes in a small valueregardless of the visible light division ratio (for example, theresolution RSO2 is approximately 1 times when the visible light divisionratio is 0% and approximately 1.1 times even when the visible lightdivision ratio is 50%).

FIG. 11 is a graph illustrating an example of relationships between thevisible light division ratio and the sensitivity GAN2, a dynamic rangeDRG3, and resolution RSO3 in a case where exposure time of the secondvisible light V2 and that of the first visible light V1 are in a ratioof 100:1. The horizontal axis in FIG. 11 represents the visible lightdivision ratio, and is the same as the description of FIG. 9, and thusthe description thereof will be omitted. The vertical axis in FIG. 11represents the sensitivity GAN2, the dynamic range DRG3, and theresolution RSO3 of the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA generated in the video signalprocessing units 17 and 17A.

FIG. 11 illustrates an example in which a difference is provided suchthat exposure time of the imaging element 152 and that of the imagingelement 151 are in a ratio of 100:1 by an electronic shutter. Similarlyto the sensitivity GAN2 illustrated in FIG. 10, it is considered thatthe sensitivity GAN2 changes in accordance with a characteristic (forexample, a linear function) that: the sensitivity GAN2 increases as thevisible light division ratio decreases, is maximum when the visiblelight division ratio is minimum (for example, the sensitivity GAN2 ismost bright at a maximum (100%) when the visible light division ratio is0%) and is minimum (the darkest at 50%) when the visible light divisionratio is 50%. This is because a result obtained by multiplying the ratio100:1 of the exposure time of the imaging element 152 to the exposuretime of the imaging element 151 by a ratio of light amount of the secondvisible light V2 to a light amount of the first visible light V1 is aratio of brightness of the second visible video signal V2VD tobrightness of the first visible video signal V1VD, and the sensitivityis determined by the brightness of the brighter second visible videosignal V2VD.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are, for example, in aratio of 100:1 as compared with a case where the exposure time of theimaging element 152 and that of the imaging element 151 are the same, itis considered that, in the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA, a difference between a bright portionand a dark portion can be furthermore clearly exhibited, and a largerdynamic range can be obtained. Accordingly, it is considered that thedynamic range DRG3 changes in accordance with a characteristic that: thedynamic range DRG3 increases as the visible light division ratiodecreases in a range larger than 0 (for example, the dynamic range DRG3is about +80 dB when the visible light division ratio is 1%) and isminimum (for example, +40 dB) when the visible light division ratio is50%. That is, in the example of FIG. 11, even at a minimum value, +40 dBcan be obtained.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are in a ratio of 100:1by an electronic shutter, for example, when the visible light divisionratio is 10% (the second visible light V2:the first visible lightV1=90:10), it is considered that a light amount incident on the imagingelement 152:a light amount incident on the imaging element 151=1000:1.That is, it can be considered that, the second visible light V2 is toobright and a dark portion is not reflected, and the first visible lightV1 is too dark and a bright portion is not reflected, and thus it isalmost difficult to obtain the resolution when the second visible lightV2 and the first visible light V1 are superimposed as compared with theexample of FIG. 10. Therefore, it is considered that the resolution RSO3changes in a small value regardless of the visible light division ratio(for example, the resolution RSO3 is approximately 1 times when thevisible light division ratio is 0% and approximately 1.02 times evenwhen the visible light division ratio is 50%).

FIG. 12 is a graph illustrating an example of relationships between thevisible light division ratio and sensitivity GAN3, a dynamic range DRG4,and resolution RSO4 in a case where exposure time of the second visiblelight V2 and that of the first visible light V1 are in a ratio of 1:10.The horizontal axis in FIG. 12 represents the visible light divisionratio, and is the same as the description of FIG. 9, and thus thedescription thereof will be omitted. The vertical axis in FIG. 12represents the sensitivity GAN3, the dynamic range DRG4, and theresolution RSO4 of the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA generated in the video signalprocessing units 17 and 17A.

FIG. 12 illustrates an example in which a difference is provided suchthat exposure time of the imaging element 152 and that of the imagingelement 151 are in a ratio of 1:10 by an electronic shutter. In contrastwith the example of FIG. 10, when a difference is provided such that theexposure time of the imaging element 152 and that of the imaging element151 are, for example, in a ratio of 1:10, for example, when the visiblelight division ratio is 10% (the second visible light V2:the firstvisible light V1=90:10), it is considered that a light amount incidenton the imaging element 152 and a light amount incident on the imagingelement 151 are substantially equal to each other by cancellation of thevisible light division ratio and an exposure time ratio. Therefore, thesensitivity GAN3 changes in accordance with a characteristic that: thesensitivity GAN3 is substantially constant as a minimum when the visiblelight division ratio ranges from 0% to 10% (in other words, when lightamounts incident on the respective imaging elements 152 and 151 do notchange much), and monotonically increases in a linear function when thevisible light division ratio is greater than 10% and no more than 50%.For example, the brightness is maximum (50%, that is, −6 dB) when thevisible light division ratio is 50%. This is because a result obtainedby multiplying the ratio 1:10 of the exposure time of the imagingelement 152 to the exposure time of the imaging element 151 by a ratioof light amount of the second visible light V2 to a light amount of thefirst visible light V1 is a ratio of brightness of the second visiblevideo signal V2VD to brightness of the first visible video signal V1VD,and the sensitivity is determined by the brightness of the brightervisible video signal.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are, for example, in aratio of 1:10 as compared with a case where the exposure time of theimaging element 152 and that of the imaging element 151 are the same, itis considered that, in the wide dynamic range video signal VVD or thehigh-resolution video signal VVDA, it is easy to obtain a difference inbrightness when the visible light division ratio decreases in a rangegreater than 0%, but a difference between a bright portion and a darkportion is unlikely to be exhibited as the visible light division ratioincreases and it is difficult to obtain the dynamic range. Therefore,the dynamic range DRG4 increases as the visible light division ratiodecreases in a range greater than 0% (for example, about +80 dB when thevisible light division ratio is 0.001%), but when the visible lightdivision ratio is 10%, the ratio 1:10 of the exposure time of theimaging element 152 to the exposure time of the imaging element 151 iscancelled, the brightness of the second visible video signal V2VD andthe brightness of the first visible video signal V1VD are substantiallyequal to each other, and the dynamic range DRG4 is minimum. When thevisible light division ratio exceeds 10%, a difference in brightnessbetween the second visible video signal V2VD and the first visible videosignal V1VD occurs again, so that the dynamic range DRG4 increases. Whenthe visible light division ratio is 50%, a ratio of the brightness ofthe second visible video signal V2VD to the brightness of the firstvisible video signal V1VD is 1:10 obtained by multiplying the ratio 1:10of the exposure time of the imaging element 152 to the exposure time ofthe imaging element 151, and accordingly the dynamic range is +20 dB.

When a difference is provided such that the exposure time of the imagingelement 152 and that of the imaging element 151 are in a ratio of 1:10by an electronic shutter, for example, when the visible light divisionratio is 10% (the second visible light V2:the first visible lightV1=90:10), it is considered that a light amount incident on the imagingelement 151 and a light amount incident on the imaging element 152 aresubstantially equal (see the above description). That is, it isconsidered that the resolution RSO4 changes in accordance with acharacteristic that: the resolution RSO4 is maximized since the firstvisible video signal V1VD based on the first visible light V1 and thesecond visible video signal V2VD based on the second visible light V2have the same brightness when cancellation of the visible light divisionratio and the exposure time ratio (1:10) occurs (for example, when thevisible light division ratio is 10%), and decreases from a maximum valuewhen the visible light division ratio is one that makes cancellationless likely to occur.

FIG. 13 is a diagram illustrating a display example on the monitor MN1of visible/IR combined video signals IMVVD, IMVVDA, and IMVVDC generatedby the three-plate cameras 1, 1A, and 1C according to the firstembodiment. The visible/IR combined video signals IMVVD, IMVVDA, andIMVVDC illustrated in FIG. 13 are generated based on imaging at anobservation part (for example, the liver and the periphery of thepancreas) of a patient that is a subject, and are displayed on themonitor MN1. In FIG. 13, a fluorescent reagent of the ICG administeredto an affected part in the patient's body in advance before surgery orexamination emits light, and the visible/IR combined video signalsIMVVD, IMVVDA, and IMVVDC indicate a location thereof (for example, anaffected part FL1). As described above, the three-plate cameras 1, 1A,and 1C can generate, for example, high-quality visible/IR combined videosignals IMVVD, IMVVDA, and IMVVDC that can allows understanding ofdetails of the observation part by a user such as a doctor at the timeof surgery or examination, and display the generated visible/IR combinedvideo signals IMVVD, IMVVDA, and IMVVDC on the monitor MN1. Such adisplay example is not limited to the three-plate camera according tothe first embodiment, and a visible/IR combined video signal generatedby a four-plate camera according to a second embodiment described latermay also be displayed on the monitor MN1 in the same manner.

FIG. 14 is a diagram illustrating a display example on the monitor MN1of visible/IR combined video signals IMVVDB generated by a three-platecamera 1B according to the first embodiment. The visible/IR combinedvideo signal IMVVDB illustrated in FIG. 14 is generated based on imagingat an observation part (for example, the liver and the periphery of thepancreas) of a patient that is a subject, and is displayed on themonitor MN1. Since the first IR video signal N2VD and the second IRvideo signal N3VD are combined in the visible/IR combined video signalIMVVDB, which are based on imaging of the first IR light N2 and thesecond IR light N3 that are separated (dispersed) into two types ofwavelength bands, it is possible to allow a user, such as a doctor, tounderstand in detail whether there is a vein or an artery in theobservation part. For example, it is known that, in a wavelength band of700 nm to 800 nm, an absorption coefficient of venous blood is higherthan that of arterial blood, and conversely, in a wavelength band of 800nm to 900 nm, the absorption coefficient of arterial blood is higherthan that of venous blood, and the absorption coefficient of arterialblood and the absorption coefficient of venous blood are reversed withthe vicinity of 800 nm as a boundary. Thus, the three-plate camera 1Bcan identify whether the blood transferred to the visible/IR combinedvideo signal IMVVDB is arterial blood or venous blood depending on aratio of an intensity of the first IR light N2 having a wavelength of700 nm to 800 nm to an intensity of the second IR light N3 having awavelength of 800 nm to 900 nm.

In FIG. 14, for example, it is indicated, by the first IR video signalN2VD, that an artery exists. As described above, for example, thethree-plate camera 1B can generate a high-quality visible/IR combinedvideo signal IMVVDB that allows a user such as a doctor to understanddetails of an observation part (in particular, presence or absence of avein and an artery) at the time of surgery or examination, and displaythe visible/IR combined video signal IMVVDB on the monitor MN1. Such adisplay example is not limited to the three-plate camera according tothe first embodiment, and a visible/IR combined video signal generatedby a four-plate camera according to a second embodiment described latermay also be displayed on the monitor MN1 in the same manner.

As described above, the three-plate camera according to the firstembodiment includes a IR prism that causes an IR image sensor to receiveincident IR light of light from an observation part, a visible prismthat causes a visible image sensor to receive incident visible light ofthe light from the observation part, and a specific prism that causes aspecific image sensor to receive incident light of a specific wavelengthband of the light from the observation part. The three-plate cameraincludes a video signal processing unit that generates an IR videosignal, a visible video signal, and a specific video signal of theobservation part based on respective imaging outputs of the IR imagesensor, the visible image sensor, and the specific image sensor,combines the IR video signal, the visible video signal, and the specificvideo signal, and outputs a combined signal to the monitor MN1.

Accordingly, with the spectral prism 13, the three-plate camera canseparate (disperse) IR light, which is specialized in a specificwavelength band (for example, 800 nm or more), that is, a fluorescenceregion of a fluorescent reagent, out of light from the observation part(for example, an affected part) to which the fluorescent reagent (forexample, ICG) is administered into a subject such as a patient inadvance at the time of surgery or examination. Therefore, thethree-plate camera can generate and output a clearer fluorescent imageof the observation part to which the fluorescent reagent is administeredand a color video by the visible light, and thus can support easyunderstanding of the affected part for a doctor or the like.

The light of a specific wavelength band is the second visible light V2having the same wavelength band as the visible light (for example, thefirst visible light V1). The video signal processing unit 17 combines avisible video signal (for example, the first visible video signal V1VD)and a second visible video signal V2VD that is based on the secondvisible light V2 to generate a wide dynamic range video signal VVD, andcombines the wide dynamic range video signal VVD and an IR video signalN1VD. Accordingly, the three-plate camera (for example, the three-platecamera 1) can display a visible/IR combined video signal IMVVD obtainedby combining the IR video signal N1VD and the wide dynamic range videosignal VVD on the monitor MN1, and thus can present a video allowing toidentify in detail a clear surgical field and a location of the affectedpart to a user such as a doctor and can appropriately support a medicalpractice for the user.

The light of a specific wavelength band is the second visible light V2having the same wavelength band as the visible light (for example, thefirst visible light V1). The video signal processing unit 17 combinesthe visible video signal (for example, the first visible video signalV1VD) and the second visible video signal V2VD that is based on thesecond visible light V2 to generate a high-resolution video signal VVDA,and combines the high-resolution video signal VVDA and the IR videosignal N1VD. Accordingly, the three-plate type camera (for example, thethree-plate camera 1A) can display a visible/IR combined image signalIMVVDA obtained by combining the IR video signal N1VD and thehigh-resolution video signal VVDA on the monitor MN1, and thus canpresent a video allowing to identify in detail a structure and alocation of an affected part having a complicated shape to a user suchas a doctor and can support appropriately a medical practice for theuser.

Further, the light of a specific wavelength band is the second IR lightN3 having a near infrared wavelength band different from the IR light(for example, the first IR light N2). For example, a wavelength band ofthe first IR light N2 is 800 nm to 1000 nm, and a wavelength band of thesecond IR light N3 is 700 nm to 800 nm. The video signal processing unit17 combines an IR video signal (for example, the first IR video signalN2VD), a visible video signal V3VD, and a second IR video signal N3VDthat is based on the second IR light N3. Accordingly, the three-platecamera (for example, the three-plate camera 1B) superimposes the firstIR video signal N2VD and the second IR video signal N3VD that are basedon imaging of a plurality of beams of IR light having differentwavelength bands to be imaged, and thus can display an IR video signalshowing a more precise condition of the affected part by reaction (lightemission) of the fluorescent reagent on the monitor MN1 together with acolor video of a surgical field, and can appropriately support a medicalpractice of a user such as a doctor.

Further, the light of a specific wavelength band is the UV light U1having a wavelength band shorter than that of the visible light V3. Thevideo signal processing unit 17 combines the IR video signal N1VD, thevisible video signal V3VD, and the UV video signal U1VD that is based onthe UV light U1. Accordingly, the three-plate camera (for example, thethree-plate camera 1C) superimposes the UV video signal U1VD, thevisible video signal V3VD, and the IR video signal N1VD that are basedon imaging of a plurality of beams of light having different wavelengthbands imaged by the image sensors of three channels, and thus candisplay on the monitor MN1 not only a color video of a surgical fieldand the IR video signal showing a condition of an affected part based onreaction (light emission) of the fluorescent reagent, but also the UVvideo signal showing a condition of the affected part obtained byimaging of the UV light, and can appropriately support a medicalpractice for a user such as a doctor.

Further, the three-plate camera according to the first embodimentincludes a first visible prism that causes a first visible image sensorto receive incident first visible light of light from an observationpart, a second visible prism that causes a second visible image sensorto receive incident second visible light of the light from theobservation part, and a specific prism that causes a specific imagesensor to receive incident light of a specific wavelength band of thelight from the observation part. The three-plate camera includes a videosignal processing unit that generates a first visible video signal, asecond visible video signal, and a specific video signal of theobservation part based on respective imaging outputs of the firstvisible image sensor, the second visible image sensor, and the specificimage sensor, combines the first visible video signal, the secondvisible video signal, and the specific video signal, and outputs acombined signal to the monitor MN1.

Accordingly, by superimposing a plurality of beams of visible lighthaving different light amounts (brightness) at the time of surgery orexamination, the three-plate camera not only can display the widedynamic range video signal VVDD having a wider dynamic range than asingle color video on the monitor MN1, but also can display a capturedvideo based on one more channel of imaging light. Therefore, thethree-plate camera can present, to a user such as a doctor, a video thatallows identification of a clear situation of a surgical field by darklyor brightly projecting the surgical field, and can appropriately supporta medical practice for the user.

Further, the light of a specific wavelength band light is the thirdvisible light V4 having the same wavelength band as the first visiblelight V1 and the second visible light V2. The video signal processingunit 17D combines the first visible video signal V1VD, the secondvisible video signal V2VD, and a third visible video signal that isbased on the third visible light to generate a wide dynamic range videosignal. Accordingly, since the three-plate camera 1D superimposes thevisible video signals of three channels having different light amounts,it is possible to display on the monitor MN1 a video having a widerdynamic range as compared with a single color video. Thus it is possibleto present, to a user such as a doctor, a video that makes it easy tounderstand a more clear and detailed surgical field, and it is possibleto appropriately support a medical practice for the user.

In addition, each of the second visible prism and the specific prism isdisposed farther from an observation part side than the first visibleprism. Accordingly, the reflecting film (for example, the secondreflecting film FLM2) disposed in the vicinity of a bonding surfacebetween the first visible prism and the second visible prism may beconfigured to have a characteristic for reflecting visible light havingthe same wavelength band as visible light incident on the first visibleprism, and thus manufacturing accuracy of the reflecting film can beimproved as compared with a case where the reflecting film has acharacteristic for reflecting IR light having a wavelength banddifferent from the visible light.

Second Embodiment

In the first embodiment, a three-plate camera equipped with the spectralprism 13 formed by bonding three prisms is described. In a secondembodiment, an example of a four-plate camera equipped with a spectralprism 14 formed by bonding four prisms will be described.

Seventh Configuration Example

In a seventh configuration example, it is assumed that a light amount ofthe first visible light V1 incident on the imaging element 151 and alight amount of the second visible light V2 incident on the imagingelement 152 are different from each other, and IR light and UV light arerespectively imaged.

FIG. 15 is a block diagram illustrating an internal configurationexample of a four-plate camera 1E according to the seventh configurationexample. The four-plate camera 1E includes the lens 11, the spectralprism 14, imaging elements 151, 152, 153, and 154, and a video signalprocessing unit 17E. The video signal processing unit 17E includescamera signal processing units 191, 192, 193, and 194, the long andshort exposure combination/wide dynamic range processing unit 21, and avisible/IR/UV combination processing unit 23E. In the description ofFIG. 15, the same components as those in FIG. 1 are denoted by the samereference signs, and a description thereof will be simplified oromitted, and different contents will be described. In the description ofa configuration in which the four-plate camera according to the secondembodiment described below is capable of imaging at least two channelsof visible light (specifically, the seventh configuration example, aninth configuration example, a tenth configuration example, and aneleventh configuration example), the long and short exposurecombination/wide dynamic range processing unit 21 and the like may notonly perform processing for having a color video having a wide dynamicrange described in the first configuration example, but also perform thehigh-resolution processing (see the above description) performed by thepixel-shift combination/high-resolution processing unit 25 in the secondconfiguration example. Further, in the description of the configurationin which the four-plate camera according to the second embodimentdescribed below is capable of imaging at least two channels of visiblelight (see the above description), the pixel-shiftcombination/high-resolution processing unit 25 may be used in place ofthe long and short exposure combination/wide dynamic range processingunit 21 and the like.

The fourth-plate camera (see FIGS. 15 and 18) according to the secondembodiment is used in, for example, a medical observation system thatirradiates a fluorescent reagent (for example, indocyanine green that isabbreviated as “ICG” in the following description) administered inadvance to an observation part (for example, an affected part) in asubject such as a patient with excitation light of a predeterminedwavelength band (for example, 760 nm to 800 nm) at the time of surgeryor examination, and that images the observation part emittingfluorescence at a long wavelength side (for example, 820 nm to 860 nm)based on the excitation light. An image (for example, a video of anobservation part) imaged by the four-plate camera is displayed by amonitor MN1 (see FIG. 13), and supports execution of a medical practiceby a user such as a doctor. Although an example in which the spectralprism 14 is used in, for example, the above-described medicalobservation system is described, the use thereof is not limited tomedical applications and may be industrial applications.

The spectral prism 14 as an example of an optical component receives thelight L2 from the observation part, and disperses the light L2 into thefirst visible light V1, the second visible light V2, the IR light N1,and UV light U2. The spectral prism 14 has a configuration in which afirst prism 41 (for example, an IR prism), a second prism 42 (forexample, a UV prism), a third prism 43 (for example, a visible prism),and a fourth prism 44 (for example, a visible prism) are bonded in order(see FIG. 19). The first visible light V1 is incident on the imagingelement 151 that is disposed so as to face the third prism 43 (forexample, a visible prism). The second visible light V2 is incident onthe imaging element 152 that is disposed so as to face the fourth prism44 (for example, a visible prism). The IR light N1 is incident on theimaging element 153 that is disposed so as to face the first prism 41(for example, an IR prism). The UV light U2 is incident on the imagingelement 154 that is disposed so as to face the second prism 42 (forexample, a UV prism). A detailed example of a structure of the spectralprism 14 will be described later with reference to FIG. 20.

The imaging element 151 as an example of a visible image sensorincludes, for example, a CCD or CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged, and an exposurecontrol circuit (not illustrated) using an electronic shutter. Theimaging element 151 is disposed so as to face the third prism 43 (forexample, a visible prism) (see FIG. 20). The imaging element 151performs imaging based on the first visible light V1 incident over firstexposure time that is determined by the exposure control circuit basedon the exposure control signal CSH1 from the camera signal processingunit 191. The imaging element 151 generates the video signal V1V of theobservation part by imaging, and outputs the video signal V1V to thevideo signal processing unit 17E.

The imaging element 152 as an example of a second specific image sensorincludes, for example, a CCD or CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged, and an exposurecontrol circuit (not illustrated) using an electronic shutter. Theimaging element 152 is disposed so as to face the fourth prism 44 (forexample, a visible prism) (see FIG. 20). The imaging element 152performs imaging based on the second visible light V2 incident oversecond exposure time that is determined by the exposure control circuitbased on an exposure control signal CSH2 from the camera signalprocessing unit 192. The imaging element 152 generates the video signalV2V of the observation part by imaging, and outputs the video signal V2Vto the video signal processing unit 17E.

The imaging element 153 as an example of an IR image sensor includes,for example, a CCD or a CMOS in which a plurality of pixels suitable forimaging of IR light are arranged. The imaging element 153 is disposed soas to face the first prism 41 (for example, an IR prism) (see FIG. 20).The imaging element 153 performs imaging based on the incident IR lightN1. The imaging element 153 generates the video signal N1V of theobservation part by imaging, and outputs the video signal N1V to thevideo signal processing unit 17E.

The imaging element 154 as an example of a first specific image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of UV light are arranged. The imaging element 154is disposed so as to face the second prism 42 (for example, a UV prism)(see FIG. 20). The imaging element 154 performs imaging based on theincident UV light U2. The imaging element 154 generates a video signalU2V of the observation part by imaging, and outputs the video signal U2Vto the video signal processing unit 17E.

The video signal processing unit 17E is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191 to 194, the long and short exposure combination/wide dynamicrange processing unit 21, and the visible/IR combination processing unit23E is implemented by the processor described above.

The camera signal processing unit 191 performs various types of camerasignal processing using the video signal V1V from the imaging element151 to generate the first visible video signal V1VD of the observationpart, and outputs the first visible video signal V1VD to the long andshort exposure combination/wide dynamic range processing unit 21. Inaddition, the camera signal processing unit 191 generates the exposurecontrol signal CSH1 for determining first exposure time of the imagingelement 151 and outputs the exposure control signal CSH1 to the imagingelement 151. The imaging element 151 controls the first exposure time ofthe first visible light V1 based on the exposure control signal CSH1.

The camera signal processing unit 192 performs various types of camerasignal processing using the video signal V2V from the imaging element152 to generate the second visible video signal V2VD of the observationpart, and outputs the second visible video signal V2VD to the long andshort exposure combination/wide dynamic range processing unit 21. Here,in the seventh configuration example, a light amount of the firstvisible light V1 incident on the imaging element 151 is different from alight amount of the second visible light V2 incident on the imagingelement 152. Therefore, the first visible video signal V1VD from thecamera signal processing unit 191 and the second visible video signalV2VD from the camera signal processing unit 192 are different inbrightness (sensitivity). In addition, the camera signal processing unit192 generates the exposure control signal CSH2 for determining secondexposure time of the imaging element 152 and outputs the exposurecontrol signal CSH2 to the imaging element 152. The imaging element 152controls the second exposure time of the second visible light V2 basedon the exposure control signal CSH2. The first exposure time and thesecond exposure time may be the same or different.

The camera signal processing unit 193 performs various types of camerasignal processing using the video signal N1V from the imaging element153 to generate the IR video signal N1VD of the observation part, andoutputs the IR video signal N1VD to the visible/IR/UV combinationprocessing unit 23E.

The camera signal processing unit 194 performs various types of camerasignal processing using the video signal U2V from the imaging element154 to generate a UV video signal U2VD of the observation part, andoutputs the UV video signal U2VD to the visible/IR/UV combinationprocessing unit 23E.

The visible/IR/UV combination processing unit 23E receives a widedynamic range video signal VVDE from the long and short exposurecombination/wide dynamic range processing unit 21, the IR video signalN1VD from the camera signal processing unit 193, and the UV video signalU2VD from the camera signal processing unit 194 and combines the signalsby superimposition, and generates a visible/IR/UV combined video signalIMVVDE. The visible/IR/UV combination processing unit 23E may output thevisible/IR/UV combined video signal IMVVDE to the monitor MN1 ortransmit the visible/IR/UV combined video signal IMVVDE to a recordingdevice (not illustrated) for accumulation.

Eighth Configuration Example

In an eighth configuration example, it is assumed that imaging isperformed by using an imaging element capable of imaging two differentwavelength bands among wavelength bands of near-infrared (IR) lightusing two channels (for example, imaging elements 153 and 154illustrated in FIG. 16), and visible light and UV light are imaged,respectively.

FIG. 16 is a block diagram illustrating an internal configurationexample of a four-plate camera 1F according to the eighth configurationexample. The four-plate camera 1F includes the lens 11, the spectralprism 14, the imaging elements 151, 152, 153, and 154, and a videosignal processing unit 17F. The video signal processing unit 17Fincludes camera signal processing units 191F, 192, 193, and 194, and avisible/IR/UV combination processing unit 23F. In the description ofFIG. 16, the same components as those in FIG. 15 are denoted by the samereference signs, and a description thereof will be simplified oromitted, and different contents will be described.

The four-plate camera according to the second embodiment (see FIGS. 16and 17) is used in, for example, a medical observation system thatirradiates a plurality of types of fluorescent reagents (for example,ICG) administered in advance to observation parts (for example, anaffected part) in a subject such as a patient with excitation light of apredetermined wavelength band at the time of surgery or examination, andthat images the observation parts emitting fluorescence at a longwavelength side (for example, 700 nm to 800 nm and 800 nm to 900 nm)based on the excitation light. An image (for example, a video of anobservation part) imaged by the four-plate camera 1F is displayed by themonitor MN1 (see FIG. 14), and supports execution of a medical practiceby a user such as a doctor.

The spectral prism 14 as an example of an optical component receives thelight L2 from the observation part and disperses the light L2 into thevisible light V3, the UV light U2, the first IR light N2, and the secondIR light N3. The spectral prism 14 has a configuration in which thefirst prism 41 (for example, an IR prism), the second prism 42 (forexample, an IR prism), the third prism 43 (for example, a UV prism), anda fourth prism 44 (for example, a visible prism) are bonded in order(see FIG. 20). The visible light V3 is incident on the imaging element152 that is disposed so as to face the fourth prism 44 (for example, avisible prism). The UV light U2 is incident on the imaging element 151that is disposed so as to face the third prism 43 (for example, a UVprism). The first IR light N2 is incident on the imaging element 153that is disposed so as to face the first prism 41 (for example, an IRprism). The second IR light N3 is incident on the imaging element 154that is disposed so as to face the second prism 42 (for example, an IRprism). A detailed example of a structure of the spectral prism 14 willbe described later with reference to FIG. 20.

The imaging element 151 as an example of a second specific image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of UV light are arranged. The imaging element 151is disposed so as to face the third prism 43 (see FIG. 20). The imagingelement 151 generates a video signal U2V of the observation part byimaging, and outputs the video signal U2V to the video signal processingunit 17F.

The video signal processing unit 17F is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191F, 192 to 194, and the visible/IR/UV combination processingunit 23F is implemented by the processor described above.

The camera signal processing unit 191F performs various types of camerasignal processing using the video signal U2V from the imaging element151 to generate the UV video signal U2VD of the observation part, andoutputs the UV video signal U2VD to the visible/IR/UV combinationprocessing unit 23F.

The visible/IR/UV combination processing unit 23F receives the UV videosignal U2VD from the camera signal processing unit 191F, the visiblevideo signal V3VD from the camera signal processing unit 192, the firstIR video signal N2VD from the camera signal processing unit 193, and thesecond IR video signal N3VD from the camera signal processing unit 194and combines the signals by superimposition, and generates avisible/IR/UV combined video signal IMVVDF. The visible/IR/UVcombination processing unit 23F may output the visible/IR/UV combinedvideo signal IMVVDF to the monitor MN1 or transmit the visible/IR/UVcombined video signal IMVVDF to a recording device (not illustrated) foraccumulation.

Ninth Configuration Example

In a ninth configuration example, it is assumed that a light amount ofthe first visible light V1 incident on the imaging element 151 and alight amount of the second visible light V2 incident on the imagingelement 152 are different from each other, and that imaging is performedby using an imaging element capable of imaging two different wavelengthbands among wavelength bands of the near-infrared (IR) light using twochannels (for example, the imaging elements 153 and 154 illustrated inFIG. 16).

FIG. 17 is a block diagram illustrating an internal configurationexample of a four-plate camera 1G according to the ninth configurationexample. The four-plate camera 1G includes the lens 11, the spectralprism 14, the imaging elements 151, 152, 153, and 154, and a videosignal processing unit 17G. The video signal processing unit 17Gincludes camera signal processing units 191, 192, 193, and 194G and avisible/IR combination processing unit 23G. In the description of FIG.17, the same components as those in FIG. 15 or 16 are denoted by thesame reference signs, and a description thereof will be simplified oromitted, and different contents will be described.

The spectral prism 14 as an example of an optical component receives thelight L2 from the observation part, and disperses the light L2 into thefirst visible light V1, the second visible light V2, the first IR lightN2, and the second IR light N3. The spectral prism 14 has aconfiguration in which the first prism 41 (for example, an IR prism),the second prism 42 (for example, an IR prism), the third prism 43 (forexample, a visible prism), and the fourth prism 44 (for example, avisible prism) are bonded in order (see FIG. 20). The first visiblelight V1 is incident on the imaging element 151 that is disposed so asto face the third prism 43. The second visible light V2 is incident onthe imaging element 152 that is disposed so as to face the fourth prism44. The first IR light N2 is incident on the imaging element 153 that isdisposed so as to face the first prism 41. The second IR light N3 isincident on the imaging element 154 that is disposed so as to face thesecond prism 42. A detailed example of a structure of the spectral prism14 will be described later with reference to FIG. 20.

The imaging element 154 as an example of a first specific image sensorincludes, for example, a CCD or a CMOS in which a plurality of pixelssuitable for imaging of IR light are arranged. The imaging element 154is disposed so as to face the second prism 42 (see FIG. 20). The imagingelement 154 performs imaging based on the incident second IR light N3.The imaging element 154 generates the video signal N3V of theobservation part by imaging, and outputs the video signal N3V to thevideo signal processing unit 17G.

The video signal processing unit 17G is configured with a processor suchas a DSP or an FPGA, for example. Each of the camera signal processingunits 191 to 193 and 194G and the visible/IR combination processing unit23G is implemented by the processor described above.

The camera signal processing unit 194G performs various types of camerasignal processing using the video signal N3V from the imaging element154 to generate the second IR video signal N3VD of the observation part,and outputs the second IR video signal N3VD to the visible/IRcombination processing unit 23G.

The visible/IR combination processing unit 23G receives the firstvisible video signal V1VD from the camera signal processing unit 191,the second visible video signal V2VD from the camera signal processingunit 192, the first IR video signal N2VD from the camera signalprocessing unit 193, and the second IR video signal N3VD from the camerasignal processing unit 194G and combines the signals by superimposition,and generates a visible/IR combined video signal IMVVDG. The visible/IRcombination processing unit 23G may output the visible/IR combined videosignal IMVVDG to the monitor MN1 or transmit the visible/IR combinedvideo signal IMVVDG to a recording device (not illustration) foraccumulation.

Tenth Configuration Example

In a tenth configuration example, it is assumed that imaging isperformed by using an imaging element capable of imaging a wavelengthband of visible light using three channels (for example, imagingelements 151, 152, and 153 illustrated in FIG. 18), and light amounts ofvisible light incident on respective imaging elements are different fromeach other. Accordingly, it is possible to generate a video signal thatallows identifying in detail a condition of a surrounding portion of asurgical field or the like according to a color video having anobservation part or a high dynamic range in a periphery thereof.

FIG. 18 is a block diagram illustrating an internal configurationexample of a four-plate camera 1H according to the tenth configurationexample. The four-plate camera 1H includes the lens 11, the spectralprism 14, the imaging elements 151, 152, 153, and 154, and a videosignal processing unit 17H. The video signal processing unit 17Hincludes camera signal processing units 191, 192, 193, and 194H, and avisible/IR combination processing unit 23H. In the description of FIG.18, the same components as those in FIGS. 15 to 17 are denoted by thesame reference signs, and a description thereof will be simplified oromitted, and different contents will be described.

The spectral prism 14 as an example of an optical component receives thelight L2 from the observation part, and disperses the light L2 into thefirst visible light V1, the second visible light V2, the third visiblelight V4, and the IR light N1. The spectral prism 14 has a configurationin which the first prism 41 (for example, an IR prism), the second prism42 (for example, a visible prism), the third prism 43 (for example, avisible prism), and the fourth prism 44 (for example, a visible prism)are bonded in order (see FIG. 20). The first visible light V1 isincident on the imaging element 151 that is disposed so as to face thethird prism 43. The second visible light V2 is incident on the imagingelement 152 that is disposed so as to face the fourth prism 44. The IRlight N1 is incident on the imaging element 153 that is disposed so asto face the first prism 41. The third visible light V4 is incident onthe imaging element 154 that is disposed so as to face the second prism42. A detailed example of a structure of the spectral prism 14 will bedescribed later with reference to FIG. 20.

The imaging element 154 as an example of a second specific image sensorincludes, for example, a CCD or CMOS in which a plurality of pixelssuitable for imaging of visible light are arranged, and an exposurecontrol circuit (not illustrated) using an electronic shutter. Theimaging element 154 is disposed so as to face the second prism 42 (seeFIG. 20). The imaging element 154 performs imaging based on the thirdvisible light V4 incident over third exposure time that is determined bythe exposure control circuit based on the exposure control signal CSH3from the camera signal processing unit 194H. The imaging element 154generates the video signal V4V of the observation part by imaging, andoutputs the video signal V4V to the video signal processing unit 17H.

The camera signal processing unit 194H performs various types of camerasignal processing using the video signal V4V from the imaging element154 to generate the third visible video signal V4VD of the observationpart, and outputs the third visible video signal V4VD to a long andshort exposure combination/wide dynamic range processing unit 21H. Inaddition, the camera signal processing unit 194H generates the exposurecontrol signal CSH3 for determining the third exposure time of theimaging element 154, and outputs the exposure control signal CSH3 to theimaging element 154. The imaging element 154 controls the third exposuretime of the third visible light V4 based on the exposure control signalCSH3.

The long and short exposure combination/wide dynamic range processingunit 21H receives three video signals having different brightness(sensitivity) (specifically, the first visible video signal V1VD fromthe camera signal processing unit 191, the second visible video signalV2VD from the camera signal processing unit 192, and the third visiblevideo signal V4VD from the camera signal processing unit 194H) andcombines the three video signals by superimposition, and generates awide dynamic range video signal VVDH. That is, by combining the firstvisible video signal V1VD, the second visible video signal V2VD, and thethird visual video signal V4VD having different brightness(sensitivity), the long and short exposure combination/wide dynamicrange processing unit 21H can generate the wide dynamic range videosignal VVDH having a wider dynamic range than the first visible videosignal V1VD, the second visible video signal V2VD, or the third visiblevideo signal V4VD. The long and short exposure combination/wide dynamicrange processing unit 21H outputs the wide dynamic range video signalVVDH to the visible/IR combination processing unit 23H.

The visible/IR combination processing unit 23H receives the wide dynamicrange video signal VVDH from the long and short exposurecombination/wide dynamic range processing unit 21H and the IR videosignal N1VD from the camera signal processing unit 193, and combines thetwo signals by superimposition, and generates a visible/IR combinedvideo signal IMVVDH. The visible/IR combination processing unit 23H mayoutput the visible/IR combined video signal IMVVDH to the monitor MN1 ortransmit the visible/IR combined video signal IMVVDH to a recordingdevice (not illustration) for accumulation.

FIG. 19 is a table illustrating a combination example of configurationexamples of the fourth-plate camera according to the second embodiment.In FIG. 19, the seventh configuration example is described withreference to FIG. 15, the eighth configuration example is described withreference to FIG. 16, the ninth configuration example is described withreference to FIG. 17, and the tenth configuration example is describedwith reference to FIG. 18. As the four-plate camera according to thesecond embodiment, as a modification of the tenth configuration example(that is, an eleventh configuration example), light incident on thefirst prism 41 may be UV light. That is, in the description of FIG. 18,the “IR light” may be replaced with “UV light”, the “video signal N1V”may be replaced with “video signal U1V”, and the “IR video signal N1VD”may be replaced with “UV video signal U1VD”.

FIG. 20 is a diagram illustrating an example of the structure of thespectral prism 14 according to the second embodiment. As describedabove, the spectral prism 14 has a configuration in which the firstprism 41, the second prism 42, the third prism 43, and the fourth prism44 are bonded in order. The first prism 41, the second prism 42, thethird prism 43, and the fourth prism 44 are assembled in order in theoptical axis direction of the light L2 concentrated by the lens 11.Here, the optical axis direction is a direction in which the light L2 isincident perpendicularly to an incidence surface 41 a of the first prism41. In the seventh configuration example to the eleventh configurationexample described above, the roles (in other words, functions andapplications) of the first prism 41, the second prism 42, the thirdprism 43, and the fourth prism 44 may be the same or different.

First, the first prism 41 is exemplified as an IR prism (see the seventhto tenth configuration examples). However, the first prism 41 is notlimited to the IR prism, and may be a visible prism or a UV prism (seethe eleventh configuration example).

The IR prism includes the incidence surface 41 a on which the light L2is incident, a reflecting surface 41 b on which a first reflecting filmFLM3 (for example, a dichroic mirror) for reflecting IR light in thelight L2 is formed, and an emission surface 41 c from which the IR lightis emitted. The first reflecting film FLM3 is formed on the reflectingsurface 41 b by vapor deposition or the like, and reflects IR light (forexample, IR light in a wavelength band of 800 nm or more) in the lightL2, and transmits light (for example, UV light of about 300 nm to 400 nmor visible light of about 400 nm to 800 nm) that is not the IR light inthe light L2 (see FIG. 8A). The IR light is totally reflected by theincidence surface 41 a after being reflected by the reflection surface41 b, and is incident on the imaging element 153 through the emissionsurface 41 c. In this way, since the IR prism is disposed as the firstprism 41, the IR component light in the light L2 from an observationpart is imaged on the most target-facing side (that is, the observationpart side) of the spectral prism 14. Compared with a case where the IRcomponent light is imaged at a rear stage side (that is, a base endside) of the spectral prism 14, attenuation of a light amount due toreflection or the like does not occur, and a condition of an affectedpart based on fluorescence emission of a fluorescent reagent can be moreclearly identified.

Next, the second prism 42 is exemplified as a UV prism (see the seventhconfiguration example). However, the second prism 42 is not limited to aUV prism, and may be an IR prism (see the eighth and ninth configurationexamples) or a visible prism (see the tenth and eleventh configurationexamples).

The UV prism includes an incidence surface 42 a on which lighttransmitted through the first reflecting film FLM3 is incident, areflecting surface 42 b on which a second reflecting film FLM4 (forexample, a beam splitter) for reflecting UV light having a wavelengthband of 300 nm to 400 nm of the transmitted light is formed, and anemission surface 42 c from which visible light having other wavelengthbands (for example, 400 m to 800 nm) is emitted. The second reflectingfilm FLM4 is formed on the reflecting surface 42 b by vapor depositionor the like, reflects UV light of light incident on the incidencesurface 42 a, and transmits the remaining visible light (see FIG. 8C).The UV light is totally reflected by the incidence surface 42 a afterbeing reflected by the reflecting surface 42 b, and is incident on theimaging element 154 through the emission surface 42 c.

Next, the third prism 43 is exemplified as a visible prism (see theseventh, ninth, tenth, and eleventh configuration examples). However,the third prism 43 is not limited to a visible prism, and may be an IRprism or a UV prism (see the eighth configuration example).

The visible prism includes an incidence surface 43 a on which lighttransmitted through the second reflecting film FLM4 is incident, areflecting surface 43 b on which a third reflecting film FLM5 (forexample, a beam splitter) for reflecting a light amount of a part of thetransmitted light is formed, and an emission surface 43 c from whichreflected visible light of the light amount of the part of thetransmitted light is emitted. The third reflecting film FLM5 is formedon the reflecting surface 43 b by vapor deposition or the like, reflectsvisible light having a light amount of a part of the visible lightincident on the incidence surface 43 a (for example, about 20% of thelight incident on the incidence surface 43 a), and transmits visiblelight having the remaining light amount (for example, about 80% of thelight incident on the incidence surface 43 a) (see FIG. 8B). The part ofvisible light is totally reflected by the incidence surface 43 a afterbeing reflected by the reflecting surface 43 b, and is incident on theimaging element 151 through the emission surface 43 c. The proportion ofthe visible light reflected by the third reflecting film FLM5 is notlimited to 20%, and may be, for example, in a range of about 1% to 30%.

Next, the fourth prism 44 is exemplified as a visible prism (see theseventh to the eleventh configuration examples). However, the fourthprism 44 is not limited to a visible prism, and may be an IR prism or aUV prism.

The visible prism includes an incidence surface 44 a on which light (forexample, visible light) transmitted through the third reflecting filmFLM5 is incident, and an emission surface 44 c from which thetransmitted light is emitted. The visible light is incident on theimaging element 152 through the emission surface 44 c.

As described above, the four-plate camera according to the secondembodiment includes an IR prism that causes an IR image sensor toreceive incident IR light of light from an observation part, a visibleprism that causes a visible image sensor to receive incident visiblelight of the light from the observation part, a first specific prismthat causes a first specific image sensor to receive incident light of afirst specific wavelength band of the light from the observation part,and a second specific prism that causes a second specific image sensorto receive incident light of a second specific wavelength band of thelight from the observation part. The fourth-plate camera includes avideo signal processing unit that generates an IR video signal, avisible video signal, a first specific video signal, and a secondspecific video signal of the observation part based on respectiveimaging outputs of the IR image sensor, the visible image sensor, thefirst specific image sensor, and the second specific image sensor,combines the IR video signal, the visible video signal, the firstspecific video signal, and the second specific video signal, and outputsa combined signal to the monitor MN1.

Accordingly, with the spectral prism 14, the four-plate camera canseparate (disperse) IR light, which is specialized in a specificwavelength band (for example, 800 nm or more), that is, a fluorescenceregion of a fluorescent reagent, out of light from the observation part(for example, an affected part) to which the fluorescent reagent (forexample, ICG) is administered into a subject such as a patient inadvance at the time of surgery or examination. Therefore, the four-platecamera can generate and output a clearer fluorescent image of theobservation part to which the fluorescent reagent is administered and acolor video by the visible light, and thus can support easyunderstanding of the affected part for a doctor or the like.

Further, the light of a first specific wavelength band is the second IRlight N3 having a near infrared wavelength band different from the IRlight. The light of a second specific wavelength band is the UV light U2having a wavelength band shorter than that of the visible light V3. Thevideo signal processing unit 17F combines the IR video signal (forexample, the first IR video signal N2VD), the visible video signal V3VD,the second IR video signal N3VD based on the second IR light N3, and theUV video signal U2VD based on the UV light U2. Accordingly, thefour-plate camera (for example, the four-plate camera 1F) superimposesthe first IR video signal N2VD and the second IR video signal N3VD thatare based on imaging of a plurality of beams of IR light havingdifferent wavelength bands to be imaged, and thus can display an IRvideo signal showing a more precise condition of the affected part byreaction (light emission) of the fluorescent reagent on the monitor MN1together with a color video of a surgical field and a UV video signalshowing a condition of the affected part obtained by imaging of UVlight, and can appropriately support a medical practice of a user suchas a doctor.

In addition, the light of a first specific wavelength band is the secondvisible light V2 having the same wavelength band as the visible light.The light of a second specific wavelength band is the UV light U2 havinga wavelength band shorter than that of the visible light (for example,the first visible light V1). The video signal processing unit 17Ecombines the visible video signal (for example, the first visible videosignal V1VD) and the second visible video signal V2VD that is based onthe second visible light V2 to generate the wide dynamic range videosignal VVDE, and combines the wide dynamic range video signal VVDE, theIR video signal N1VD, and the UV video signal U2VD that is based on theUV light U2. Accordingly, the four-plate camera (for example, thethree-plate camera 1E) superimposes the UV video signal U1VD, the firstvisible video signal V1VD, the second visible video signal V2VD, and theIR video signal N1VD that are based on imaging of a plurality of beamsof light having different wavelength bands imaged by the image sensorsof four channels, and thus can display on the monitor MN1 not only thecolor video having a wide dynamic range of a surgical field and the IRvideo signal showing a condition of the affected part based on reaction(light emission) of the fluorescent reagent, but also the UV videosignal showing a condition of the affected part obtained by imaging ofthe UV light, and can appropriately support a medical practice for auser such as a doctor.

In addition, the light of a first specific wavelength band is the secondvisible light V2 having the same wavelength band as the visible light(for example, the first visible light V1). The light of a secondspecific wavelength band is the second IR light N3 having a nearinfrared wavelength band different from the IR light (for example, thefirst IR light N2). The video signal processing unit 17G combines thevisible video signal (for example, the first visible video signal V1VD)and the second visible video signal V2VD that is based on the secondvisible light V2 to generate the wide dynamic range video signal VVDD,and combines the wide dynamic range video signal VVDD, the IR videosignal (for example, the first IR video signal N2VD), and the second IRvideo signal N3VD that is based on the second IR light N3. Accordingly,the four-plate type camera (for example, the four-plate camera 1G) cansuperimpose the first IR video signal N2VD and the second IR videosignal N3VD that are based on imaging of a plurality of beams of IRlight having different wavelength bands to be imaged, and furthersuperimpose the first visible video signal V1VD and the second visiblevideo signal V2VD to generate a color video having a wide dynamic range,and thus can display on the monitor MN1 a color video having a widedynamic range of a surgical field and the IR video signal showing a moreprecise condition of the affected part by reaction (light emission) of afluorescent reagent and can support a medical practice for a user suchas a doctor.

In addition, the four-plate camera according to the second embodimentincludes a first visible prism that causes a first visible image sensorto receive incident first visible light of light from an observationpart, a second visible prism that causes a second visible image sensorto receive incident second visible light of the light from theobservation part, a first specific prism that causes a first specificimage sensor to receive incident light of a first specific wavelengthband of the light from the observation part, and a second specific prismthat causes a second specific image sensor to receive incident light ofa second specific wavelength band of the light from the observationpart. The fourth-plate camera includes a video signal processing unitthat generates a first visible video signal, a second visible videosignal, a first specific video signal, and a second specific videosignal of the observation part based on respective imaging outputs ofthe first visible image sensor, the second visible image sensor, thefirst specific image sensor, and the second specific image sensor,combines the first visible video signal, the second visible videosignal, the first specific video signal, and the second specific videosignal, and outputs a combined signal to the monitor MN1.

Accordingly, by superimposing a plurality of beams of visible lighthaving different light amounts (brightness) at the time of surgery orexamination, the four-plate camera not only can display the wide dynamicrange video signal VVDD having a wider dynamic range than a single colorvideo on the monitor MN1, but also can display a captured video based ontwo more channels of imaging light. Therefore, the four-plate camera canpresent, to a user such as a doctor, a video that allows identificationof a clear situation of a surgical field by darkly or brightlyprojecting the surgical field, and can appropriately support a medicalpractice for the user.

In addition, the light of a first specific wavelength band is the thirdvisible light V4 having the same wavelength band as the first visiblelight V1. The light of a second specific wavelength band light is the IRlight N1 having a wavelength band longer than that of the first visiblelight V1. The video signal processing unit 17H combines the firstvisible video signal V1VD, the second visible video signal V2VD, and thethird visible video signal V4VD that is based on the third visible lightV4 to generate the wide dynamic range video signal VVDH, and combinesthe wide dynamic range video signal VVDH and the IR video signal N1VDthat is based on the IR light N1. Accordingly, since the four-platecamera superimposes the visible video signals of three channels havingdifferent light amounts, it is possible to display on the monitor MN1 avideo having a wider dynamic range as compared with a single colorvideo. Thus it is possible to present, to a user such as a doctor, avideo that makes it easy to understand a more clear and detailedsurgical field, and it is possible to appropriately support a medicalpractice for the user.

In addition, each of the first visible prism and the second visibleprism is disposed farther from the observation part side than the firstspecific prism and the second specific prism. Accordingly, thereflecting film (for example, the third reflecting film FLM5) disposedin the vicinity of a bonding surface between the first visible prism andthe second visible prism may be configured to have a characteristic forreflecting visible light having the same wavelength band as visiblelight incident on the first visible prism, and thus manufacturingaccuracy of the reflecting film can be improved as compared with a casewhere the reflecting film has a characteristic for reflecting IR lighthaving a wavelength band different from the visible light.

Although various embodiments have been described above with reference tothe drawings, it is needless to say that the present disclosure is notlimited to such examples. It will be apparent to those skilled in theart that various alterations, modifications, substitutions, additions,deletions, and equivalents can be conceived within the scope of theclaims, and it should be understood that such changes also belong to thetechnical scope of the present disclosure. Components in variousembodiments described above may be combined freely within a range notdeviating from the spirit of the invention.

INDUSTRIAL APPLICABILITY

The present disclosure is useful as a three-plate camera and afour-plate camera that generate and output a clearer fluorescence imageof an observation part to which a fluorescent reagent is administered,and support easy understanding of an affected part for a doctor or thelike.

What is claimed is:
 1. A three-plate camera, comprising: an IR prismthat causes an IR image sensor to receive incident IR light of lightfrom an observation part; a visible prism that causes a visible imagesensor to receive incident visible light of light from the observationpart; a specific prism that causes a specific image sensor to receiveincident light of a specific wavelength band of light from theobservation part; and a video signal processing unit that generates anIR video signal, a visible video signal, and a specific video signal ofthe observation part based on respective imaging outputs of the IR imagesensor, the visible image sensor, and the specific image sensor,combines the IR video signal, the visible video signal, and the specificvideo signal, and outputs a combined video signal to a monitor.
 2. Thethree-plate camera according to claim 1, wherein the light of thespecific wavelength band is second visible light having a samewavelength band as the visible light, and wherein the video signalprocessing unit combines the visible video signal and a second visiblevideo signal that is generated based on the second visible light togenerate a wide dynamic range video signal, and combines the widedynamic range video signal and the IR video signal.
 3. The three-platecamera according to claim 1, wherein the light of the specificwavelength band is second visible light having a same wavelength band asthe visible light, and wherein the video signal processing unit combinesthe visible video signal and a second visible video signal that isgenerated based on the second visible light to generate ahigh-resolution video signal, and combines the high-resolution videosignal and the IR video signal.
 4. The three-plate camera according toclaim 1, wherein the light of the specific wavelength band is second IRlight having a near-infrared wavelength band different from that of theIR light, and wherein the video signal processing unit combines the IRvideo signal, the visible video signal, and a second IR video signalthat is generated based on the second IR light.
 5. The three-platecamera according to claim 1, wherein the light of the specificwavelength band is UV light having a wavelength band shorter than thatof the visible light, and wherein the video signal processing unitcombines the IR video signal, the visible video signal, and a UV videosignal that is generated based on the UV light.
 6. A three-plate cameracomprising: a first visible prism that causes a first visible imagesensor to receive incident first visible light of light from anobservation part; a second visible prism that causes a second visibleimage sensor to receive incident second visible light of light from theobservation part; a specific prism that causes a specific image sensorto receive incident light of a specific wavelength band of light fromthe observation part; and a video signal processing unit that generatesa first visible video signal, a second visible video signal, and aspecific video signal of the observation part based on respectiveimaging outputs of the first visible image sensor, the second visibleimage sensor, and the specific image sensor, combines the first visiblevideo signal, the second visible video signal, and the specific videosignal, and outputs a combined video signal to a monitor.
 7. Thethree-plate camera according to claim 6, wherein the light of thespecific wavelength band is third visible light having a same wavelengthband as the first visible light and the second visible light, andwherein the video signal processing unit combines the first visiblevideo signal, the second visible video signal, and a third visible videosignal that is generated based on the third visible light to generate awide dynamic range video signal.
 8. The three-plate camera according toclaim 6, wherein each of the second visible prism and the specific prismis disposed farther from an observation part side than the first visibleprism.
 9. A four-plate camera comprising: an IR prism that causes an IRimage sensor to receive incident IR light of light from an observationpart; a visible prism that causes a visible image sensor to receiveincident visible light of light from the observation part; a firstspecific prism that causes a first specific image sensor to receiveincident light of a first specific wavelength band of light from theobservation part; a second specific prism that causes a second specificimage sensor to receive incident light of a second specific wavelengthband of light from the observation part; and a video signal processingunit that generates an IR video signal, a visible video signal, a firstspecific video signal, and a second specific video signal of theobservation part based on respective imaging outputs of the IR imagesensor, the visible image sensor, the first specific image sensor, andthe second specific image sensor, combines the IR video signal, thevisible video signal, the first specific video signal, and the secondspecific video signal, and outputs a combined video signal to a monitor.10. The four-plate camera according to claim 9, wherein the light of thespecific wavelength band is second IR light having a near-infraredwavelength band different from that of the IR light, wherein the lightof the second specific wavelength band is UV light having a wavelengthband shorter than that of the visible light, and wherein the videosignal processing unit combines the IR video signal, the visible videosignal, a second IR video signal based on the second IR light, and a UVvideo signal based on the UV light.
 11. The four-plate camera accordingto claim 9, wherein the light of the first specific wavelength band issecond visible light having a same wavelength band as the visible light,wherein the light of the second specific wavelength band is UV lighthaving a wavelength band shorter than that of the visible light, andwherein the video signal processing unit combines the visible videosignal and a second visible video signal that is generated based on thesecond visible light to generate a wide dynamic range video signal, andcombines the wide dynamic range video signal, the IR video signal, and aUV video signal that is generated based on the UV light.
 12. Thefour-plate camera according to claim 9, wherein the light of the firstspecific wavelength band is second visible light having a samewavelength band as the visible light, wherein the light of the secondspecific wavelength band is second IR light having a near-infraredwavelength band different from that of the IR light, and wherein thevideo signal processing unit combines the visible video signal and asecond visible video signal that is generated based on the secondvisible light to generate a wide dynamic range video signal, andcombines the wide dynamic range video signal, the IR video signal, and asecond IR video signal that is generated based on the second IR light.13. A four-plate camera comprising: a first visible prism that causes afirst visible image sensor to receive incident first visible light oflight from an observation part; a second visible prism that causes asecond visible image sensor to receive incident second visible light oflight from the observation part; a first specific prism that causes afirst specific image sensor to receive incident light of a firstspecific wavelength band of light from the observation part; a secondspecific prism that causes a second specific image sensor to receiveincident light of a second specific wavelength band of light from theobservation part; and a video signal processing unit that generates afirst visible video signal, a second visible video signal, a firstspecific video signal, and a second specific video signal of theobservation part based on respective imaging outputs of the firstvisible image sensor, the second visible image sensor, the firstspecific image sensor, and the second specific image sensor, combinesthe first visible video signal, the second visible video signal, thefirst specific video signal, and the second specific video signal, andoutputs a combined video signal to a monitor.
 14. The four-plate cameraaccording to claim 13, wherein the light of the first specificwavelength band is third visible light having a same wavelength band asthe first visible light, wherein the light of the second specificwavelength band is IR light having a wavelength band longer than that ofthe first visible light, and wherein the video signal processing unitcombines the first visible video signal, the second visible videosignal, and a third visible video signal that is generated based on thethird visible light to generate a wide dynamic range video signal, andcombines the wide dynamic range video signal and an IR video signalgenerated based on the IR light.
 15. The four-plate camera according toclaim 13, wherein each of the first visible prism and the second visibleprism is disposed farther from an observation part side than the firstspecific prism and the second specific prism.